Hi, Ever Since My Gallbladder Was Removed I've Been Experiencing

Hi, Ever since my gallbladder was removed I've been experiencing lots of stomach issues. Specifically I have experienced stomach tremors upon eating, burning stomach pain through to my back, change in bowel habits and trouble eating food to the point that I dropped 25 lbs. Most recently I've noticed a lot of mucus in my stool and it goes back and forth between clay colored and black. Is this chronic gastritis?