Severe digestion problem. Every day!

Hi one day suddenly I felt uneasiness when I had fish and vomited. From next day onwards I felt fatigue, fever, weakness and digestion problem. Slowly I was feeling pain on stomach walls at random places and my weight decreased from 64 to 59kgs in one month. I visited doctor and undergone all tests endoscopy, colonoscopy, CT scan, stool test, hydrogen breath test, liver profile, thyroid test and then doctor said everything normal and also he said you are suffering from IBS. I get lot of burps, heart burn, pain on random places in stomach due to gas. I am taking Razo D and probiotics and still I have digestion problem along with excessive gas. Also I am on BRAT diet. Please suggest what is my real issue. I have to eat a lot to maintain my weight 59 to 60 kgs. I lost fatigue and weakness but excess gas creates lot of problem mainly heart burn, it is daily problem and I am fed up with it. I am also getting neck pain every day