ankylosing spondilitis sufferer with bowels not working:Help!

I have been having problems with bowel movements over the last year or so. I have done psyllium, bentonite, salt water cleanes (for a day or two at a time), changed diet, had a barium enema to check for blockage..none seen. In the last couple days it has gotten worse. I can feel and hear things happening but then nothing is coming out. The muscles don't seem to be pushing anything out and there is no feeling of having to go. Needless to say I am feeling pretty bloated all the time. Fleet laxative works but hate to use them. Any ideas of why this is happening and how I can get things going again? I should add that I have ankylosing spondilitis and my spine is pretty much fused solid. I have wondered if there could be nerve damage but my md says he doesn't think so. Could this be connected to my problem?