Definitely find a high quality protein supplement. It's good extra nutrition that's easy to digest for IBDers with compromised guts, but if you're weight training, you need it even more.
I would disagree with your doc, though, and would recommend either a whey protein isolate or an egg white protein. If you get the whey, be sure to get an isolate and not a concentrate as it's almost lactose free and easier to digest.
Diagnosed with ulcerative colitis spring 1999.
Maintenance dose sulfasalazine. Probiotics, l-glutamine, vitamin D and fish oil caps. George's aloe vera juice. Oregano oil antibiotic, antiviral, antifungal. Mostly grain-free and dairy-free diet. Long-term remission with only minor blips.