I use Canasa suppositories when needed. Whether it's UC or Crohn's, if you've got inflammation in the area, and it's helping, I say go for it. I occasionally get so inflammed around my anus that I bleed slightly, without a fistula or anything else. I think the skin just kind of gives up and I end up with very small tears. I try not to let things get to that point, but a day of more frequent than normal bms can do it. I try to use Calmoseptine (OTC, request from your pharmacist) when ever I start to see irritation. That helps with the burning and itching, and protects the skin. Usually a couple days of that brings things back under control, assuming that it was just a bad day or two and not an extended period of D.
The sitz bath was a good suggestion. I find that they may sting at first, but once you get past the first few seconds, it feels really good. I have skin tags, which makes it hard to wipe. (Too many nooks and crannies!) So it's one of the few times I feel really clean, too.
I would discuss the situation with your doctor. At the very least, your current treatment isn't controlling all your inflammation. And you have a legitimate reason to think that you may have been misdiagnosed. (Which happens a lot with UC and Crohn's.) If you can't get answers to your questions, get a second opinion.