I Am 75 Yrs. Old And Have Been Having Problems

I am 75 yrs. old and have been having problems with reacting to everything I eats or even touch. I am only able to eat a few things without getting a reaction. (All my reactions are delayed, not immediate reactions). for the past 6-7 months, I have become very, very bloated and very constipated, only going once or twice a week. I am wondering if you might have an idea what is causing this. the doctor has ordered a small bowel upper GI test, which requires you to drink a fair amount of a contrast, which I may react to so I am wondering if there is another way to figure this out. thank you for your help.