What does a contraction feel like?

To me, it felt like exactly what it was: a muscle contraction. I felt the uterus "bunching up" then relaxing. It was a lovely feeling, actually. If you get pains that feel like a menstrual cramp, that's the cervix "thinning out" and opening up ready for the baby to be born. All in all, the pain wasn't awful; it was a very natural, beautiful experience for me.