I Periodically Have A Burning Pain On The Right Side

I periodically have a burning pain on the right side of my abdomen. It's killing me now, feels like it's burning, and making me feel like i'm going to faint. It usually goes away, but today it hasn't. It really doesn't fit the appendicitis scenario, but what else could it be? I have Ulcerative Colitis and have for 41 years. It does not feel like this. My gallbladder was removed over 20 years ago. thanks