I'd suggest calling the doc (I hope you did- your post is from long before I joined up today) and letting her know you are having intense GI symptoms. They won't want you to continue a drug that causes such misery. Weaning from Zoloft was no problem for me. I cut my dosage by half every week until I was taking 12.5 mg every other day before I stopped. Coming off the Cymbalta is much worse than that was.
If the Zoloft works for depression symptoms, theoretically the pain from depression should abate also? I certainly hope so. I took Cymbalta for lumbar nerve impingement pain, and it did help that.
It's my hope that in the interim, you've gotten better!