how can I tell what i can eat or not

I've been having a panic attack basically regarding what I can eat or not, how can I tell if a food is bad for? is it going to the bathroom right after eating it, is it getting random pains 5mintues after eating? how can I really tell if a food is bad for me, what are the signs.
Sometimes it takes 5 minutes to show bad signs, while other times it takes 7 hours, everyone is different. You can keep a diary of what you can and cannot eat, if you want to use food to keep symptoms down. If you can cook for yourself, it is better, though it is very time-consuming.
There are some very typical Crohn's avoidance foods. To be avoided mostly when experiencing a flare up. Foods with husks, seeds, shells, thick fibrous fruit or vegetable skins, popcorn, and particularly corn. You should stick with cooked veggies until you can figure out what agrees with you and what doesn't.

Some food choices are strictly subjective. It will require some trial and error, but if you're having severe bouts of anxiety over everything you put in your mouth, it could be a complicated process. There is a Crohn's diet called the low residue diet. You can try it for a week or two and see how your digestive issues are, and then just keep adding foods you like and see how your react.
My daughter was diagnosed Feb. 19/07, (13 yrs. old at time of diagnosis), with Crohn's of the Terminal Illium. Has used Prednisone and Pentasa. Started Imuran (02/09), had an abdominal abscess (12/08). 2cm of Stricture.
Started Remicade in Feb. 2014, along with 100mgs. of Imuran.