I Have Been Taking Xanax For 4 Months And Have

I have been taking xanax for 4 months and have been recently having stomach problems. I am never hungry but when I do eat I feel sick and have to rush to the bathroom for bowel movements. My dr. Is telling me it is just stress but nothing seems to be getting better. I am not stressed. I have dropped 10 pounds in 2 weeks and I don't think its all in my head. Is this just stress or could something else be going on.