Foamy burps, diahrea, pain lower right abdomen

I need help. I have been suffering with this for a long time and I just ran out of health insurance. I had blood test, colonoscipy, and stool test and all have come back negative. I have had diahrea after I eat certain foods, like spegetti with meat sauce and mexican food. Also I have uncomfortable pain on the lower right side of my abdomen. Also right under my rib cage center right on my stomach. I have just recently started foaming alot after I eat. I have lost my appetite and have lost 30 pounds in maybe four - five  months. My poop also smells very weird sometimes like a chemical. I have tried fiber and they do not help. WHat do I have. The doctors say it is Ibs but it is hard to believe that stress could make you foam poop all the time and have pain in your abdomen.