Eric,
I understand you are upset and concerned about the cause of your twitching, but you are way off base on just about everything you said and you are scaring yourself and others needlessly. You are very confused and ill informed and I will explain. If your twitching is from MS, that has nothing to do with taking or coming off
Lexapro.
First, you should never stop any medication without first consulting with your doctor and getting proper instructions for getting off of it. All SSRI's as many many medications, require a slow withdrawal with a slow tapering of the medication over a period of months. 2 1/2 weeks is too fast.
Second, I have no clue why your doctor prescribed Lexapro for GAD. It is not and antianxiety medication, it is an antidepressant and OCD medication. Did you have depression due to GAD?
NOTE: St Johns Wart is used by some for mild depression symtoms, but not clinical or major depression. Again, the property of this herb is an antidepressant, not an antianxiety remidy, so why would you take it if you don't have depression?
Third, Tardive dyskinesia is not a side effect of Lexapro or any of the SSRI's. There are other medicines where high dose, long term use of that drug can cause tardive dyskinesia, which is not reversible, but Lexapro is not one of them.
Fourth, I know hundreds of people on lexapro, I took it myself, and I know of no such twitching side effects as you suggest. The only thing you mention that can be a rare side effect of Lexapro is tingling and that would occur while you were on the medication, not a side effect of stopping it.
Fifth, while a GP can prescribe any medication, heck, a dentist, a surgeon, an ENT, etc., can prescribe medications, but it is not wise to use them or your GP for psychiatric medications when you are going to be taking them for more than a few weeks or months. GPs are not fully trained in psychiatric medications and they need to be prescribed by a psychiatrist who is fully trained in the medicine and the side effects and the proper ways to come off the medications, etc.
Sixth, SSRI's do NOT cause brain damage, you are really getting carried away with your fears. You need to work with the proper doctor and do the research on any medication before you take it.