I think I have Social Phobia. I can function but with extreme pain, and each day I feel like giving up?

Aww, I'm sure the TA was able to tell that you are shy and didn't think you were being disrespectful! I think it's good that you sent the note to thank her and let her know what you couldn't say in person. It's the type of thing anyone would appreciate but not everyone would respond. Try not to feel bad because you didn't do anything wrong. You obviously want help so think about seeing a therapist.