Ever tried therapy so you can beat it permanently without medication, given your success thus far without professional help?
Health anxiety is really common. MS is difficult to diagnose under the best of circumstances. It does involve a lot more than muscle twitching though. What is your caffeine intake like? do you exercise? Eat well? Sleep well? Not everyone has to take medication for anxiety but you will need to work on it in some way. Breathing exercises, meditation, yoga? Could you talk to a therapist?