I am so sorry that this happened to you! I think you are right, though... it is likely that your miscarriage is not related to the 6mp or the UC. I am currently pregnant (17 weeks), and I am on Asacol. My positive story is that we tried to get pregnant for four years. No infertility treatment worked, so we gave up. Three months later, I turned up pregnant.
During the time we were trying, I did a ton of research, and everything said that UC does not affect fertility or pregnancy. My GI concurred. Still, I always blamed the infertility on my UC (regardless of what the science was telling me), and obviously, I was wrong about that because I still have UC and now I am pregnant. My GI tells me that his hospital, the Cleveland Clinic, has a ton of 6 mp babies and even a few Remicade babies.
Hang in there... this will happen for you! I have a friend who has two healthy children after 7 miscarriages... and she is a perfectly healthy woman, just a little older in age (like me). Sometimes, the Lord works in mysterious ways.