H.L.
What JB said. Same for me. When I asked my doctor how he had come to that conclusion, he said that if the meds made me feel better, then it was IBS. A few years later, I learned that I have a gluten sensitivity, which is often misdiagnosed as IBS. GI stuff is so very tricky. The key is to make sure that you have a doctor who is committed to your thorough care. Even when the symptoms don't always add up to a name, your ailments must be addressed. Get a good doctor, and tell that doctor EVERYTHING that is going on with your body, even the things that you think are not connected. If you are experiencing anything in your life that could be stressful or otherwise life-changing, tell it! Make sure that you have a doctor who will look at everything and address even the "minor" details with you.
Good luck!