I had a c-section but I was having contractions the week before - not frequent enough to go in, but I felt really terrible. It was kind of like horrible period cramps? Nothing sharp, but my back and abdomen would ache so badly and I wouldn't be able to get comfortable at all. If I remember right, I had diarrhea and definitely nausea. I actually pulled out my pain meds left over from surgery (baby-safe, of course) to get through that week since it was right before my scheduled c-section.
Also for the record, this was my first delivery so I have no metric for what it might have felt like sans J-pouch.
If I were you, I would definitely go right in to your OB to have them check on you, especially since you're only 37 weeks.