Hello Seems I Am Most Likely Allergic To A Food

Hello seems i am most likely allergic to a food product. Having a problem with complete liquid stools. been a problem for a long time, used to be a half hr after breakfast. and that was the end but as of late whole tummy is upset- with gas movement in tummy constantly. and seems as of late I could even regurgitate. Do also have major sinus problems could this factor in with a heavy mucous flowing down back of the throat? Oh also a 47 year old diabetic.