hello there nyxin. I understand your anxiety situation. I think you are the first person I have seen that is so open about the anxiety thing playing such a part in all this. Of course anxiety and stress just make us go to the bathroom more, and then the more we go the more anxious we get. LOL I am not trying to be crass or unfeeling, but sometimes humor helps.
BUt, seriously now....I read on here a couple days ago about another person having similar symptoms, and all the feedback messages mentioned appendix, as in appendicitis. I am not saying this to upset you. I am trying to help. One of the messages said that you could have these types of symptoms for quite awhile sometimes, before actually finding out it is appendicitis. Perhaps when you speak to the doctor again, if you havent mentioned that "burning" feeling, that you mention it. Of course if you already did, and he has done all of the things above, maybe you could just keep track of it, and just keep bugging your doctor.
I REALLY hope you have, or do, begin to feel better. I have crohns disease, so I know what you are feeling. The anxiety, nervous stomach, frequent BMs, etc..
Please take care, and let us know if and when it does stop, and how you are doing.