I know the pain your having. I went through the same thing caused by remicade. I feel your pain.
However the doctor took me off remicade put me on humira and back on imuran. The arthritis pain is all gone. Though i was in the hospital for 2 days last week, so I didn't take imuran (6mp) for 3 days and the arthritis came back with a angry.
I've yet to hear someone taking both MTX and Imuran. I suggest doing some research see if other's have. If you still don't feel comfertable enough speak with your family doc, or get a second opion. It's very important your comfertable with what your doing and taking.
Good luck, I really hope you get some relief soon