Keep a food diary and see if there is a co-relation between what
you eat and symptoms that appear. Chronic constipation, sedentary life style building up gas in the gut, inflammatory bowel disease (like the Crohn's disease you have), food rich in sulfites (molasses, dry powder, pickles, tinned shrimp, cookies, crackers, and readymade pie dough), cabbage, raddish etc also cause bloating and nausea.
Please consult your PCP for primary examination followed by proper referral.
Take care!