Hey, Dawn; I'm sorry to hear you're dealing with this!
I'm currently fistula free but lived with an R/V fistula for 4 years. My doctor advised no tampons for exactly the reason C-jay outlined; holding fecal material in the vagina for any length of time is not good. For most of the 4 years I simply needed a liner, and many days that wasn't even dirtied. Toward the end I needed pads, but that was after complications had arisen.
Sex is fine, but you might want to follow some precautions. Lubricant is good, but avoid anything scented or being inserted up into you (other than the obvious! ); wash afterward (my doctor said it was a good idea for my husband to wash as well). If you are sore or have a yeast infection avoid sex for the time being as it can be very uncomfortable and/or make the problem worse. Oh, and use gentle, unscented soap for washing; it really makes a difference.
No antibiotic; actually, I tried to avoid these unless they were absolutely necessary as I had too many problems with yeast infections and they would make those worse. I didn't have an abscess or problems like that, however. I think this advice varies depending on the type & location of the fistula.
I underwent several attempted repairs, most of them very minor, which is why I agreed to try them. Toward the end, however, my particular fistula grew very large and was causing major problems so I had to have a rather extensive surgery to fix the problem. Should this become an issue for you, I'm glad to answer any questions.