Concerning 'facial migraine', I'd like to contribute some information. Seeing an ENT for headaches is not incredibly common though it's not at all a bad decision (so long as you're also being followed by a neurologist specializing in headache disorders--by that I mean that if you are sick enough to need to see a specialist like an ENT who could diagnose secondary headaches then you probably ought to be seeing a headache specialist). In my opinion you seem to have had a fruitful visit because a otolaryngologists (who knows a heck of a lot about
sinus problems) to rule out the possibility that your headaches stem from sinus issues.
But receiving the diagnosis of "facial migraine" is not especially helpful. The IHS (int'l headache society) classification system (ICHD-II) does not list an known headache disorder with that name nor anything particularly close to it (unless you arterial dissection or certain uncommon psychiatric diseases). As the name implies, facial migraine--to the best of my knowledge--is a non-technical symptomatic diagnosis. By this I mean that the diagnosis describes your symptoms (facial pain presumably) rather than its cause or any particular comorbidity ("the coexistence of one disorder with another that occurs more commonly than by chance"). But just because his diagnosis may not be what the IHS would use it doesn't mean his treatment is incorrect--amiltriptyline can be a very effective Rx). But if you continue to have problems that diagnosis doesn't appear to be associated with an prognosis or insight into its progression.
In my lay (not medically trained but very experienced with headaches) opinion, it seems likely that you may be suffering from something called Trigeminal neuralgia. If you don't already know, neuralgia means pain that is caused by a nerve--the trigeminal nerve in this case.
"The trigeminal nerve is the fifth cranial nerve, a mixed cranial nerve responsible for sensory data such as tactition (pressure), thermoception (temperature), and nociception (pain) originating from the face above the jawline; it is also responsible for the motor function of the muscles of mastication, the muscles involved in chewing but not facial expression."
Neuralgia, especially from the trigeminal nerve, is a very common cause of extracranial headaches. Thankfully that means it's very treatable. Now, I want to reiterate that I am in no way qualified to diagnosis your headaches but I speak from experience and what I'm saying might be a good subjec to simply ask your doctor about.
Nerve pain is often treated with antiinflammatories, nerve blocks (anesthetic injections surrounding the problematic nerve(s)), and potential muscle relaxants. From what I've seen (and from reason), nerve blocks tend to be very effective as they literally block the pain signals sent by the nerve. In most cases a headache specialist will not use this treatment as a first course of action.
Anyway, just "some" information that MAY be relevant to your problem. In any case I do recommend seeing a headache specialist if you continue to have problems.
Best of luck and well wishes,