It sounds like you may have developed C.Diff from the antibiotics. I am going through the same thing. Go to your doctor and mention this possibility to him/her. Also, you can look up C.Diff online and get lots of info to see if you think you do actually have it. Good Luck!!
When you'll go to the doctor, you can mention antibiotics and opportunities for food-born or water-born infection. You can propose above mentioned tests.
No I did not travel or drink suspicious water. I'm 24 and live at college with roommates. I share a bathroom that doesn't get cleaned as much as it should so maybe I picked up some kind of bacteria.
Hard to say if it was antibiotic or not. Anyway, you have chronic diarrhea now, and you have to find a cause.
1. stool test may reveal microorganisms (parasites, like Giardia, are known to cause prolonged mild diarrhea)
2. if stool test will be negative, you can have a breath test, from which it can be seen, if you have bacterial overgrowth in the small or large intestine.
3. next thing is elimination diet (improvement after gluten-free diet speaks for celiac disease, improvement after milk-free diet speaks for lactose intolerance). Celiac disease can be diagnosed only with upper endoscopy, though.
4. With sigmoidoscopy, diverticles in last part of the colon may be found. With colonoscopy and biopsy, inflammatory bowel disease can be confirmed.
If you are after 50, two rare colitises exist: colagenose colitis and ischemic colitis, which both cause diarrhea.
I've just listed all main causes of chronic diarrhea; from what you have said, you probaly don't have IBS. Doctor will probably suggest above tests one after one.
Have you traveled in November or October, have you drunk any suspicious water...?