How to identify contraction?

Well for me, it felt like very horrible menstrual cramps. Before my labour contractions started, I had the cramps for 1-2 nights before but it went away after half hr , one hr when I walked. I also timed it when it stated and stopped with an app and it was very regular and getting more painful. My water didn’t break and I didn’t lose my mucus plug before I felt the contractions. But it’s different for everyone. My sisters felt like back pain at the start.