It sounds like you have been through the ringer, I hope that your fistula heals - or at least improves. I have had a very similar experience to yours; I have crohns, and have had an ileostomy since 93 and have been dealing with scar tissue since about 95, I have already had a couple of surgeries to remove the stricures, but they tend to come back. I am hoping that eventually they will stay away. Since September I have had a bad abscess that had to be removed and packed (not at all a pleasant experience) and a bad blockage, they tried to dilate me for a couple of months but the opening has gotten narrower, so narrow that now they can't dilate me at all, and I am having surgery in a couple of weeks. I was really hoping to go 5 years between surgeries but only made it 3 and a half.
There are a couple of web sites out there that sell ostomy intimate apparel. If you do a search for ostomy underwear you should find them. I have never actually bought any of it, I just like the regular stuff and my ex didn't care about the bag so I didn't think much about covering it up. As for a bathing suit...I also buy regular suits, but it is hard to find ones that work. I really like the tankinis from llbean - they are high wasted enough, lined and also come in patterns which is key to hiding the appliance. Plus, having a two piece makes using the bathroom frequently to keep the bag empty at the beach or pool much easier than pulling on and off a wet bathing suit. I also love the surfer shorts...I hope they never go out of style :) Good luck, I hope things get better for you!
Happiness is a journey not a destination - Souza