Does anyone have experience with being diagnosed with Crohn’s disease while still serving in the military?

Not personally, but I had a fellow squad leader who was. It was many years ago, and he was ultimately discharged because of it. I don't know about today. His was really bad, and I understand there are varying degrees of it. Good luck.

I had a peer in I Corps that had it. Bottom line, there's the treatment and then the big question. Is it manageable? To what extent? What's needed to maintain "extent"? At that point, the Med types make a determination of retention or medical discharge. Since either way the MIL side will flick you over to VA at some point, make sure you keep a copy of every scrap of medical record, the various letters coming and going about it, etc. File with VA at your earliest opportunity as that's when the money clock starts.