I experienced this a few times, the first time I woke up with horrid cramps that never let up for a few hrs.... I could barely talk or breathe, my dr sent me in and I was hooked to the monitor where it showed irritable uterus , I was having small contractions on top of each other literally for hrs on end.... Excruciating!!! I'm also a smaller person with a small belly and my dr said there's just no room and I feel everything.... So when I had 2 other spells since that time, I just got lots of rest abs hydration and eventually they let up :/
Hopefully this is ur start of labor though and NOT that!!! Lol. Just wanted to share though:/