One of the symptoms of a flare-up of IBD is a fever. During the night, the fever may spike several times, causing body temperature to raise and lower. If you're covered up with a sheet and blanket, you'll probably start to sweat. At first you may not wake up, but then your body temperature will lower, you'll start to feel cold and uncomfortable, and then you'll wake up soaking wet.
The best way to deal with night sweats is to be prepared for them. Try not to turn too many lights on when you get up, it will only wake you up further. Have a change of clothes and bedding close at hand, as well as some cold water to drink. You can also try sleeping on some thick towels or an extra blanket to avoid getting your bedding wet.