Are you sure they wanted you on both at the same time? That's the first time I've ever heard that combination mentioned. I've heard of one biologic used in combination with
Methotrexate and
6MP but never two biologics together.
The only information I was able to find about the two being used together was this:
Also tell your doctor about all the medicines you take.
You should not take HUMIRA with ORENCIA® (abatacept), KINERET® (anakinra), REMICADE® (infliximab), ENBREL® (etanercept), CIMZIA® (certolizumab pegol), or SIMPONI® (golimumab).
http://www.humira.com/ulcerative-colitis/default.aspx
Talk to your doctor again and find out for sure. Also ask them for any studies about the two being used together before going through with it.