Hey DOW...so sorry you're having a bad time. Sometimes when it rains it pours, huh. Here's a link about the ibuprofen... http://www.mayoclinic.com/health/dru...N=side-effects
My GI tract will tolerate a little of it and no more than that once in a blue moon and that's it. The only way to tell what was causing it is to try the ibuprofen again...if you really want to know.
Then again, there could be something going on and the ibuprofen is just aggravating it.