What could be a problem if just the physical fact of speaking for a long time causes severe stress symptomes?

Hi. If you would say something like just go to a shrink, doctor or whatever, my answer is simple. Been there, done that, I've actually been to some pretty serious institutions. He-he. :) But nobody finds me crazy, or finds any serious abnormalities at all. Yeah, I do some antidepressants as a sleep aid. It doesn't solve my general problem. I used to teach some private language cles for a long time where I had to speak for hours in a row. Well, I had to quit for the same reason I asked this question. Long time speaking (say more than 10 mins) to anyone gets me awfully stressed. Not anxious or afraid. No! Even speaking to close friends. Just mere fact of doing it. It developed over time and felt like nervous exhausttion, Ok. So, Again, My questions is whether anybody has any ideas as to technical psychiatrical, biochemical or whatever aspects of this condition. By the way. I have insomnia(do huge doses of amitriptyline to be able to sleep) and tinnitus also. So I'm not that nornal in fact. But I'm not a disabled at all. Actually, I do full time physical job presently which kind of helps me to relax. Any Ideas and suggestions are welcome.