I also have IBS and suffer from depression and anxiety. They often seem to go hand in hand, don't they? I have been taking antidepressants for about 9 years; (have had IBS for about 15). I feel that the antidepressants do help my IBS in the long run because they help me with my anxiety. Anxiety can wreak havoc on the digestive system anyway; how much worse for those of us with IBS.
I also have tried many different antidepressants - Buspar, Celexa, Lexapro, Zoloft, Cymbalta, and Paxil. For me, the Paxil seems to work the best. Zoloft gave me terrible digestive problems which no person with IBS needs to deal with! The other antidepressants just didn't seem to work as well as the Paxil. However, antidepressants seem to be an individual thing - what works for one person may not work as well for another. My doctor was so sure Cymbalta would be great for me, but it hardly helped me at all.
I don't recall any negative effects on my IBS from changing medications. I'm sorry to hear you have multiple digestive issues. Having just one is bad enough! I hope you can find something that works for you.