Ulcer trouble

I had my RNY surgery on De.c 7th. Everything seemed to be going good until I went to pureed foods. I started having pain after eating and nausea. Last friday I had to have an endoscopy and my surgeon found an ulcer. I am now taking Previcid 2 times a day but still have pain after eating. Did anyone else have this problem and if so do you have any suggestions?