Sounds like it is related to food or medicine. I'd do a little detective work and see if it happens every time after you X? Do you have any cramping or other problems? are you eating Mexican once a week? do you tolerate dairy well -- I have to take a Lactaid pill or I'll get in trouble eventually, a day or two later, with certain dairy products and I don't always remember/think of it so the problem gets worse over time.

If you cannot discover the pattern or what is causing it, then I'd go talk to your doctor, just to see if s/he can. Keep a food diary for a week or two and see what happens?