sorry to hear that you are dealing with chronic pain from bruxing. Grindcare was the only thing that worked for me, and I tried EVERYTHING. Very very unfortunate that you let someone botox your masseters (I hope they didn't botox your temporalis as well?). Works at best temporarily, has bad long term effects that have kept the FDA from approving this usage, and complicates future diagnosis and treatment with the gold standard, EMG and makes the closest thing I know of to a cure, bruxism interruption, much more difficult.
A better way imho is to diagnose with something less damaging than Botox, like a few nights of muscle relaxants. The best way to diagnose is with EMG. I think you should really read the wikipedia entry on bruxism, even though I am sad to see that they are no longer including Grindcare by name in the list of 3 diagnostic tools. Grindcare is incredibly expensive, but I have tried most of the others and imho you can get the surest diagnosis with Grindcare, with the key bonus of the only effective treatment I have found for chronic bruxism. The sleep study EMG's are usually a cruel ineffective joke, where a tech slaps at best a single electrode in the general direction of your temple and often getting false negatives if someone botoxed you.
If you do use a sleep study to try to diagnose bruxism, make sure that your sleep study is covered by your insurance. Then learn where the temporalis muscle is by placing the pad of your index finger over your temple, clenching, and learning to feel where the temporalis muscle is that has clenched along with your masseters. Next, make sure that the sleep study tech places the lead over your temporalis, not someplace else. For those who have been snookered into getting their temporalis muscle botoxed, you need to find the remnants, or muscles under the hairline that have taken over the job of the atrophied temporalis, and hope it's enough for the sleep study EMG machine to track. People who have been botoxed before sleep studies that also monitor for bruxism often get false negatives for bruxism, I think.
Bite guards are great for protecting your expensive dental work from getting bruxed to bits. They only worsen, unfortunately, the effects by bruxism on the TMjoint (simple lever). This could be why you have more joint inflammation and pain after getting a bite guard. They do work well to protect your dental work, so I am not recommending that you stop using it, even if you were sold it as though it would cure some undiagnosed malocclusion, that was supposedly causing your bruxism, and supposedly will stop it. Malocculsion is one of the rarer causes of chronic bruxism, imho. Moreover, whatever sets off bruxism, once it becomes chronic, you could even cure the original trigger, but that won't stop the chronic bruxism! Because it is now neurmuscular and chronic! So chronic bruxism needs to be addressed before it causes too much pain and damage. If your bite guard is thin and has a little give, it probably isn't adding much to the damage that chronic bruxism can cause to the TMjoint eventually, and it could protect your dental work while you look for a way to stop the chronic bruxing.
I agree completely with wikipedia that chronic bruxing has usually become subconscious and habitual, a neuromuscular or sleep disorder that will not get cured by making assumptions that you have misaligned teeth (malocculsion) or are responding to anxiety that you can stop by psych, willpower, stress reduction, etc. If you can try stress reduction without spending $$ that's a good idea, because it will work if your bruxism is not yet chronic. Otherwise, the only thing I trust is Grindcare. Although FDA approved, Grindcare is being sued by USA patent holders who want a piece of Grindcare's exploding business (exploding everywhere but here in the litigious patent world, which is completely degenerated from it's original goal of protecting innovators while insuring that others can eventually use their innovation for more innovation).
On the subject of your headaches: I would not assume yet that your headaches are a direct result of bruxism, although they sometimes are. But many people with, for example, hereditary migraine, hope against hope that bruxism is their real problem, when it might not be at all. The kind of migraine-or-worse headaches I get from bruxing are not only from bruxing - I have damaged nerves from the broken neck that are doing reverse conduction, which means spreading a lot of inflammation due to damaged nerves sending false 'ouch' messages all the time. I still don't get the whole brain lining inflammation and trigeminal nerve strangling by inflammation unless both my bruxism and reverse conduction are completely out of control. By stopping the bruxism with Grindcare's biofeedback mode, I have a real life again sometimes, after having been bed ridden and literally dying for years, on massive druges to keep me semi out of pain. Grindcare let me stop having to drug myself to semi-consciousness.
But I have to doubt that many people have enough disparate sources of inflammation to cause my kinds of headaches. You really want to get effective EMG (you can chart Grindcare over many nights for a crystal clear diagnosis) to see if chronic bruxism is even your main problem. And you want to stop letting people who sell treatments make assumptions about your diagnosis so they can sell you the treatment that they happen to know about. A good diagnosis can save you years of dead ends or pain or $$. Tracking your daytime headaches over many weeks, and seeing if there is a direct correlation with how much bruxing you did the night before is possible with Grindcare. If Grindcare's biofeedback mode stops the headaches, then you know that your correlation is actually causation. But this is something that you need to track accurately over weeks or months, which Grindcare lets you do easily with a USB connection to simple line graphs, from a device the size of an ipod nano, with an EMG lead instead of earplugs.
Did the Botox make a difference temporarily? Which muscles did you get botoxed? I got too much (3 full vials one year, both to masseters and to temporalis muscles). Taking a few nights of muscle relaxants seems to me the safest treatment-as-diagnostic-tool, not Botox. Since you quickly develop a tolerance to muscle relaxants (and don't want the systemic effect), they are best just for diagnosis, and not as good as EMG you can do for many nights (like Grindcare). The problem with Botox is that it might give you some relief from the effects of subconscious bruxing, so it can work as another treament-as-diagnosis tool, but it will also be only temporary for chronic bruxism, with some long term, permanent, and unknown effects that make it not worthwhile (hence no FDA approval for bruxism). An additional reason that Botox should not be used to diagnose or treat chronic bruxism is that the muscle atrophy (and reduced sensation) it causes, complicates EMG diagnosis and treatments like Grindcare's biofeedback.
Everybody bruxes during various phases of our lifes, in childhood, during hormonal changes, during some kinds of stress. This is not anything you need to diagnose or treat. It is important to diagnose it, however, if the bruxing becomes chronic and damaging to teeth, TMjoint, and nerves. EMG is the only sure way I know to get a good diagnosis, and should be on many successive nights (and you would not believe the other diagnostic tools out there that I have tried, including jaw arc analysis, other esoteric efforts by dentists and pain doctors, and the usual guards, nti devices, etc.).
As for stopping chronic bruxism, I don't know of anything that works while enhancing your restorative sleep except Grindcare. I kind of liked the dentist who patented a mouthguard containing ampules of hot pepper liquid, that you would burst when bruxing, and would hopefully stop you - the guy was really trying, although I don't see how being woken up by 5 alarm chili heat could be any better for your sleep than an increasingly loud audible warning tone (the headband) would be for your sleep or marital partner.
So, if I were you and still experiencing what you think might be pain from chronic bruxism, I would try a short course of muscle relaxants before bed, and keep a diary of how you feel the next days. And I would like to know how many vials of Botox you got, what patterns of injections, in how many sessions, and to what muscle groups. Also, don't automatically assume that chronic bruxism is causing your headaches. You could investigate them in tandem, although a clear diagnosis of whether or not you have chronic bruxism will make the investigation easier.