http://en.wikipedia.org/wiki/Serotonin
My guess is that part of what is going on is that you've gone from sufficient serotonin on the med because it inhibits reuptake, to an insufficient amount in your system off the drug, or a dysregulation of it because your system has been dependent on the help from the SSRI for so long that it can't regulate well, or at least is taking a while to adjust to regulating again.
Serotonin regulates bowl movements, and you're messing with it. My guess is that it may continue indefinitely or it may suddenly start to get better, depending on your body's capacity to make more.
I went off anti-depressants, but I didn't do it until after I had completely changed my diet to organics, low flash point oils, no dyes and preservatives, and much more raw plant material than was ever a part of my diet as a young person. I didn't have bowel complications once I went off the drugs, but I suspect my body was making more of what it needed naturally with less load on the systems overall.