I am sorry you developed a fistula, and understand how you feel. I too have a fistula. I developed mine just over a month ago, after SRS. I was still in the hospital when it was discovered. They told me that the tissue around the fistula was too swollen, so it couldn't be repaired until the tissue was healthy and the stitches would take. Since I didn't have any symptoms of infection, they kept me in the hospital under observation, and was going to release me. They said it had about a 20% chance of healing on its own, but would most likely need to be repaired from within the rectum. Then I developed an infection, and I had to get another operation to bypass my large intestine called an ileoscopy. I was devastated, but at least it is temporary, for about 8 weeks. till then, my waste is passed directly from my small intestine into a bag. After my ileoscopy, they said the fistula has a 50% change of healing on it's own. Why they raised the chances of it healing on it's own from 20 to 50% I don't know, maybe because no stool is being processed thru my large intestine anymore.
Anyway, they told me not to dilate more than a few inches until it heals or can be repaired, but I am going in the full length of my smallest dilator, which is 4 inches. I have gone thru so much I don't want my vagina to close up entirely. after I am all back to normal, with the fistula repaired, and my small intestine rejoined to my large, I will consider my options for vaginal depth. I am afraid of any more operations, and right now am thinking if I can keep about 10 cm or 4 inches of functional depth, that will be ok. I hear that's not too far from the average for us. I will just have to adapt my sexual positions.
anyway, I was told I had a 20% chance of it healing by itself at first, then a 50% chance after they diverted my stool away from the large intestine.