You know, there are people who get their bachelor's degrees in the 60s and 70s, just because they want to, so why should you be any different.

If you want your PhD, get it, no matter how long it takes, but don't get it at the price of your health. Take it slowly and it will happen, maybe not as quickly as you had hoped, but, it will happen.

If you take the attitude that you are going to get your degree, no matter how long it takes, maybe that will take the stress off a bit and lessen the effects of the Crohn's.