You could ask for a pelvic MRI which would probably show the fistula if you had one. At the minimum, it would give you peace of mind.
I recently had an enlarged right labia, asked for an MRI, and it showed a fistula from my anal area (I have a jpouch) through the perineum. The MRI did not show the abscess, but when I went to the surgeon, he found a 3 cm. abscess in the right labial area and lanced and drained it. It still drains mostly blood/mucous now and then, but not a lot, and I don't see a correlation with jpouch activity. I'm taking flagyl and levaquin now to keep things "at bay" until I go to the cleveland clinic in a couple weeks to see what they might be able to do for the fistula.
Hope you get answers soon.