Extremely Painful BM's

Have been having extremely painful BM's, when I can even have them.  Not sure if it is hemmorhoids, constipation, fecal impaction, polyps or something else preventing easy BM.  Something is pressing on bladder and causing throbbing.  Have taken enemas and mag citrate, with only minor relief.  Starting to be concerned I am getting anal cancer.  Have others had this kind of problem with remicade and 6mp? 

Didn't know inflammation could get this bad. Thanks for your reply.

I have been in a flare for 2 1/2 years. The only break I have had was for about 2 1/2 weeks after the third infusion of remicade. The mag citrate has now caused watery d which has taken away some of the severe pressure, but I am very sore. Same thing happened last week. But after two days, all blocked up again. Tried canasa and anucort and proctofoam in the past to no avail. Taking precsription miralax every night. Been about 9 months since last scope which showed Active UC - no improvement at all from prior year.