positive self image

I have SA. I get extremely tense and nervous in social situations for no apparent reason. The only thing is, I don't think I have a negative self image. I never catch myself saying that I can't do anything, or that im stupid, or that im awkward or anything like that. So what now? I've heard that for some therapies, you are supposed to develop an automatic positive reaction to any negative thoughts. The thing is, I don't have these thoughts. Just the fear. Anyone else experience this or have any more information? Could this mean that I just have hyperthyroidism or something like that? The social anxiety has only made me depressed once or twice (for a few hours).