Acid in esophagus, why?

I have had a case of ulcers (off and on) since 1995. I recently had a flare up again and started taking prevacid. A week ago, I had a gallbladder attack which lead me to find this wonderful web site. (thx for cure zone!) Now I am taking dandelion, watching what I eat and giving my gallbladder time to heal from it's inflammation before doing a flush, next week. What I don't understand is that even with the daily prevacid, after some meals I still have a tremendous amount of acid coming up from my stomach into my esophagus, which is very painful and uncomfortable. Why isn't the prevacid enough? Could it be this is actually bile coming up from the gallbladder because of indigestion? Does anyone have experience with this?