What do true contractions feel like?

I can't figure out if I'm having contractions or just braxton hicks, it honestly feels like I have stomach ache but it's this tightening sensation in my stomach that's kind of dull and it radiates sort of to my back and is putting pressure on my bladder, it's making me feel like I have to pee! But I don't know what this is! They feel like menstrual cramps but more worse....

Anyone feel this before?

36w2d.