How do you kno its contractions?

Quick question i don't want to sound dumb but I want to ask rather then not asking? I never got to feel normal contractions only when I was induced at the hospital, so how do you feel contractions outside of being induced? I have been having alot of lower back pain and my stomach gets hard and I feel like it's hard to walk sometimes because my bladder hurts as well. This just started happening today im 33 weeks. I am timing it to see if there's a difference but im like what am I looking for im not to tolerant with pain either?