Extreme pain before bowel movements.

I am a 25 year old woman that is healthy.  I have been on a methadone program for two years and birth control.  For years I experience horrible pains for about a half hour until I pass a bowel movement.  During the passing I experience intense pain from the amount and sometimes size.  Also, I break out in sweat during the movement and the pain is agonizing and almost hemmoroid causing.   For the most part I have bowel movements every day.  However about once a week have the very painful, extremely large movements.  I notice they are often after I take my methadone in the morning but have had these pains most of my life as I remember.  Any idea if this is colitis, IBS, or something else altogether? Help would be greatly appreciated.

[sammy520]

Have you looked into following?
Crohn's Disease, Diverticulitis/Diverticulosis