I've had the same thing happen - I had a surgery to 'lay
open' the peri-anal fistula I had, and it didn't heal until I went on remicade... before the remicade (I was in the process of applying for it), it was barely healing at all, but once I was on the meds, literally, the day after my 1st infusion, it started healing very quickly.
I feel your pain, its very frustrating having these things healing so slowly (or not at all) - I had to have a secondary surgery because the abscess behind the fistula was not draining fast enough through the surgery incision, so I had to have a mushroom catheter put in to drain the excess. I hope you get some speedy healing soon!