I had a similar problem about 15 years ago. It started with severe diarrhea, cramping, and it lasted 2 months. I was in the ER 3 times with it, and no one could come up with an answer. I lost 15 lbs, and could not even keep water, jello, or anything in me. I had bloody stools and it scared me to death. I finally saw a specialist and he said it was anxiety and stress. HOWEVER, you really need to find the cause of this, as it can lead to low potassium levels, heart palpitations, etc.
I had very low potassium levels and they gave me an IV for it. It took several months to gain back the weight, and I swore I would never let anxiety get to me like that again.
Please see you dr ASAP, and dont take OTC meds in case you do have an infection. Are you under a lot of stress or suffer from anxiety??