That is how I was with meat - gave it up and lots of things have disappeared that gave me grief before.
It has taken me ages to sort things out but now have found giving up meat, cows milk and lettuce (of all things) have made life easier. I can eat yoghurt and cheese and other greens like spinach.
My son also has Crohns and he is Vegan and the thing he has problems with is Nuts and Seeds so all of us are different.
Good Luck with Slimming World.