What do contractions feel like?

Is anyone able to describe to me what a contraction feels like? Here’s the context: I have been getting Braxton Hicks contractions since about 20 weeks (currently 33 weeks) which feel like painless tightening of my uterus. The sensation feels like my uterus is balling up, but it doesn’t hurt. Last night I woke up three different times with what felt like menstrual cramps in my lower abdomen, but it wasn’t associated with the “balling up” or tightening sensation. At first I was concerned these were contractions, but then assumed since my uterus wasn’t tightening that they weren’t. They haven’t been regular at all (I haven’t even felt it since getting out of bed) and I haven’t had any bleeding and my baby is still moving a lot so I’m not really concerned. Just curious what exactly I’m feeling.