I'm taking otc caffeine/diuretic for competition; also imodium (loperamide) for the loose stools it cause. is that counterproductive? can i take both at same time?

Neither: Dehydration and potential fluctuation in electrolytes could impact your performance.

What started?: If constipation and that is resolved stop the meds. Fluids, prunes, bran and natural approach can be effective on preventing constipation. Right now your GI tract is confused!

Yes and Yes.: Doesn't sound like diarrhea will help you in your competition at all. Best to not take either and get plenty of rest and be well-prepared.