If you want to try stopping BCPs, I'd recommend considering a copper IUD. It is effortless, cheap contraception that doesn't use hormones. My copay covered it and it was done in the office. They may talk to you about the one with hormones, but the copper one works just fine without the side effect of hormones. The only issue is that for the first six months or so I had heavy menstruation, and I did need iron replacement for the first time ever. The one with hormones doesn't cause as much of that, but hormones are in the news again as being dangerous ... cancer, blood clots, these are real risks.
IBS won't go away even if you stop taking your birth control pills. IBS is a chronic condition which can be better or worse depending on how you control it
Most of people get IBS by over using medicine or stress so in your case the birth control might have trigger it so you will have to stop it asap and hope that it's not to late and that your stomach flora will restore