Epigastric pain

I am 54 years old male. My major symptom was a strong epigastric pain and CT showed that my common duct was blocked by gallstone. I had ERCP and the stone was removed about one month ago (I am not sure if they done sphincterotomy too). My bilirubin and liver functions returned to normal, but I still have epigastric pain one month after ERCP (not as strong as before ERCP, but strong enough that I can’t work), indigestion, nausea, no appetite and generally I don’t feel well. I have pain for most of the time but it is worse after meal (the worsening starts about 1 hour after meal and usually last for 3-5 hours) although I only eat small low fatty meals.
I am not sure if the gallbladder causes my problems or the problems are caused by common duct, i.e. infection introduced by ERCP procedure or it is something else.
I would appreciate if you can give me your opinion about my problems and recommend which tests I should do.
Thank you very much for your time.