Another possibility is maybe you have a vestibular disorder. They can visually test for Nystagmus, but it is better if you are videotaped by a professional to see if you present with it. If that's the case, it would explain most everything except maybe the swallowing (which, my gosh, with everything you've got going on, you have every right to feel anxious).
I had a caloric test & tilt table test done by my ENT & they came back normal, but I was lucky & had a really fantastic neurologist who told me that while he didn't know what was wrong, he believed that it was real. Heart palpitations were caused by dropping bp. Headaches were caused by eye strain. I was fighting so hard to keep my balance (without realizing it) that my muscles were all tired & would spasm. Slurred speech. Forgetting words. Trouble concentrating. Trouble with keeping track of time (I could read a clock, but would struggle to tell without a clock whether 30 minutes or 3 hours had passed). Trouble adding (even though I scored a 780/800 on the GRE). Crashing into walls (couldn't judge where the wall was exactly). Felt like I was spinning, sometimes like the room was spinning & rarely like both I & the room were spinning in different directions. Falling off stairs, ladders, etc. because suddenly everything would start spinning. Trouble turning door knobs, twisting off lids, etc. I could go on. In my case, it was due to a birth defect that was impacting the balance center of my brain (which did show up on my MRI), but there were people at the vestibular rehab center where I went with all sorts of problems causing the vestibular issues -- stroke, birth defects, sports injuries, all sorts of things.
It's not as common as thyroid disorders, but it definitely could include a bunch of your symptoms. Treatment is specialized physical therapy where basically they torture you by making you dizzy & teaching your body how to get better at keeping its balance. You need a doctor to diagnose a vestibular disorder, but you could try a home self-test. It's not 100%, but it does work in a lot of cases & doctors/physical therapists do suggest it so it's not just some crazy out there thing. Keep in mind that SAFETY is very important. DO NOT do this alone. Do not do it by any glass, tables, heaters or anything else you would keep a small child away from. If you can, do it by a bed or something soft on the off chance that you start to fall. What you do is stand one foot directly in front of the other, cross your hands over your chest and stand there until you have your balance, & then close your eyes. See if you can keep your balance for a few seconds. If you START TO FALL, immediately open YOUR EYES, put your hands out & do whatever you need to catch your balance (that's also why another person can be helpful). If you are totally unable to do it & fall over right away, I would say to go get tested. Usually either a neurologist or ENT would test for this. I think neurologists are generally better, but an ENT at a teaching hospital would be good too. If you can do it for only 2-3 seconds, then maybe keep it in mind that it could be an issue. If you can do it for 5 seconds or more, you are totally golden & it would be unlikely that you have any sort of vestibular problems (but only a doctor can make a definitive diagnosis).
I hope you don't have that, but it's such a simple test I share it with just about anybody. My friend's mom had similar symptoms & I shared this self-test with her. She couldn't do it for even one second (she's post stroke). Now she's in therapy & is doing much better. I know several other people who also did the self-test & 2 of them also failed & turned out to test positive for Nystagmus as well.
Other than that, I agree with Carmen about maybe trying to get tested for fibro. Seizures usually would be only for a short period of time & it sounds like your issues are more constant. I think probably if you have something neurological going on it is more likely something rare.