Shark,
I had a serious bout with ulcerative colitis in the past which is a form of IBS. The whole time I had my colitis I continued to workout and consume my bodybuilder diet. It is hard to say if whey will directly effect you, as towards the end I did have periods of bloating, but I think the best thing for you to do is continue exploring your condition. Go see a GI. It sucks but you may have to undergo a sigmoidoscopy or even a colonoscopy to be sure. If your going to continue eating like a bodybuilder try a whey isolate or a whey (such as optimum) which includes aminogen to aid in digestion. Right now dairy and caffeine may aggravate the IBS. I sincerely hope your condition is nowhere as serious as mine, but get yourself checked out brother. Please also never hesitate to ask me any questions about this, as I have accumulated more knowledge than I would ever want to know on this subject.
Every man's life ends the same way. It is only the details of how he lived and how he died that distinguish one man from another.