I would head to your doctor. I had the same problem and finally couldn't stand it anymore and went to my doctor. It was found that I had IBS and acid reflux (I always had terrible heartburn at night-even hours after eating or not eating anything spicy). I wasn't too surprised b/c both IBS and acid reflux "run" in my family and several of them suffer from it. I now take Zelnorm (2x a day) and Aciphex (1x a day) and have found relief. Your doctor may send you to a gastrologist too, which may not be a bad idea.
Good luck!