possibly so, but he needs you to hang in there and be strong for him. Cats are sponges for our emotions and he is picking up on your upset and anger.If he does only have IBD we put him through a very traumatic experience for no reason,
Try something to get your mind off this so you can move forward for him - physical exercise, meditation, deep breathing, music,...---oh by the way, regarding stress, try some cat music for him.
There's spotify, youtube, RelaxMyCat and MusicFor Cats. Additionally there are licki mats that might be of help to him
The LickiMat - Food Puzzles for Cats