I Have Pain In My Lower Left Side/back. It Can

I have pain in my lower left side/back. It can range from a dull ache or pressure to debilitating pain. A heating pad and Pamprin helps but it isn't menstrual related. If it is spastic colon, there are no other issues as far as bowel movements go. I will have cramps in my side and back muscles the entire time and I can feel them being knotted up. I had my gallbladder removed 10 years ago, if that matters. Also, after eating only a few bites I will get the feeling of being so full I get sick. I gag and fear I will vomit, especially when sitting up or bending at the waist in general.