I can definitely say that birth control pills CAN cause IBS. I was put on the them at age 18 for poly-cystic ovaries. I gained 60pds in three months, developed anxiety attacks and horrible IBS to the point that I was in the bathroom with runs, cramping and nausea every night and got no sleep. My doctor insisted it was not the pill and changed me three times over a year. I finally gave up and quit the pill. I knew myself enough to know that I had been a socially active, healthy girl all my life and that the pill had to be the problem. Immediately all the systems went away upon stopping the pill, I moved to Charleston and got my life back.
Several years later the poly-cystic ovaries forced me to try the pill again. This time, the same side effects happened. Again, they tried me on several new pills. This time b/c i was much older, the systems got worse. Upon stopping the pill, the symptoms improved, but the IBS moved in permanently.
I have started taking digestive advantage and exercising regularly which has all but stopped the IBS. I will get it within a few days of my period. Good luck. NO pill for me again.
Always grateful for the blessings I do have!