I understand your frustration, believe me. I use to get migraines from age 12-18, three to four times a week that were so debilitating I couldn't work out. The doctors gave me different medicine each one made me feel worse.I tried eating certain foods, drinking a lot of water, you name it, I tried it. Eventually I went to a chiropractor myself who did an xray, it showed my spine was curved to the left causing nerve impingement. I went just one time and I haven't had a migraine,12 years later.
What I'm saying isn't to suggest self diagnoses but in a way I am because you yourself know when something isn't right and no one else. If you ask any doctor how long they have been one for they will say they have been "practicing" medicine for a certain amount of years. I like to say I was "practicing" on finding the correct doctor to help me find a solution and I did because it effected my life completely.
I'm a personal trainer (and a damn good one) but not a doctor so I really suggest you keep looking for the right one. It "sounds" to me like you may have an electrolyte imbalance or vitamin deficiency when you say your muscles are twitching. I have my clients (with this issue or muscle cramps) make sure they are getting enough taurine.
In the cell, taurine keeps potassium and magnesium inside the cell, while keeping excessive sodium out. In this sense, it works like a diuretic.Because it aids the movement of potassium, sodium, and calcium in and out of the cell, taurine has been used as a supplementation for epileptics, as well as for people who have uncontrollable facial twitches.
The neck issue could be many things so keep a log of your physical activity and diet to chart days your neck issues are worse. Keep us up to date on your progress. The reason I became a trainer was to help people who feel like I use to feel, who are looking for answers when they can find none. The right people are out there to help you if you just keep looking.