Welcome to the forum. I have seen some others talk about Rituxan. I have never taken it myself, but I'm sure the ones that have will come along to give their experience with it.
It sounds like you are in a nasty flare right now. I hope the Cellcept works for you this time and you will start feeling alot better soon. Please keep us updated and take care. Hope to hear from you again soon. You will be in my prayers.