With what you've been through, it could be anything.....
As Kazbern said, strong antibiotics can really wreck your intestinal tract, even a healthy person. I agree with yogurt with active cultures myself. I would give all this to the doc and proceed from there.
Diagnosed (FINALLY) UC Sept 09/Diagnosis amended 5-3-10 to Crohn's
openia DX July 2010
Taking Pentasa 500mg/8x/day
Bentyl as needed
1000 mg Vitamin C