I Have Developed A Digestion Problem. I Feel Sick After

I have developed a digestion problem. I feel sick after drinking one 12 oz beer. My stomach becomes boated, I feel nauseous and I have trouble falling asleep. I feel lethargic the following day. I'm experiencing problems after eating pizza and cheese. I become bloated and burp slot. I also have gas. Is this a type of food allergy? I am 48, a female. I compete in triathlons, I run ultra races. I stand at 5'2 and weigh 129. Should I be concerned?