I agree, definitely don't change your moniker, unless it is something like excatholicmat. If you were always LDS, why was your moniker catholicmat? Oh wait, maybe you were a catholic mormon (Easter, Christmas).
Anyway, welcome back, and keep coming to cougarblue. Welcome back to church as well, I know it can be a tough transition, because my roommate just came back after several years. Hang in there!