I've never had the exact problem you're describing but I do know that my disease definitely affects the muscles in the lower GI track. I have to take three stool softener/laxatives a day to stay somewhat regular. With MS the GI track slows down thus leading to the maximum absorbion of water and constipation.

Your situation sounds more like a lack of coordinated muscle activity and spasms. The suggestion of taking a muscle relaxant, i.e. Klonopin/Clorazepam, might not be a bad idea. I would also suggest a strong laxative suppository for results within 30 minutes. It works primarily on the lower GI track muscles and will hopefully clean you out.

Also try some hot Camomile tea as this may help your muscles relax.

Don't be embarrassed about bringing a serious subject like this up as it is something many many of us deal with on a daily basis. You are NOT alone.