Hello, Erwin. I have been wondering how you were doing. I'm sorry to hear that you are having this uncomfortable problem at night. It sounds like a gas problem to me, and maybe it's related to your Crohn's. Maybe not. It could be that you have developed an intolerance to some foods due to your untreated bowel inflammation. You might try an elimination diet to see if there is any one culprit. I would start with the most common ones, like lactose and gluten.
Lactose intolerance is really easy to discover, and very simple to manage - you just take a lactase enzyme pill or two before meals. To discover if you are lactose intolerant (almost every adult is, to some degree) you can ask your regular DR, or maybe drink a glass of milk on an empty stomach and see what happens.
Gluten intolerance is more challenging to diagnose and more challenging to manage. I tried a gluten free diet for 3 weeks to figure out if I was sensitive to gluten, and by the time 2 weeks had passed the evidence was clear to me. I haven't eaten any gluten (except by accident or special choice) in more than a year. I feel a lot better.