For the time being, probably best to avoid raw vegetables, nuts, seeds, lettuces, and fruits with skins. Really well-cooked vegetables may be ok for you. You'll just have to try and see what you can tolerate. Hopefully when you improve you can reintroduce many more foods to your diet. Peeled apples or pears or peaches might be ok, or might not, for you. Applesauce, white bread, rice, bananas, potatoes, yogurt, things like that are often 'safe' foods, but everybody's different.
As for the diagnosis, having the antibodies means you *might* have Crohn's, but as gumby said, you need a colonoscopy with biopsies, and perhaps an MRI of your small bowel, in order to make the diagnosis. In those tests they can gauge severity too, and get you started on proper medication if you indeed have Crohn's.
Good luck with the tests and let us know how you're doing.