Contraction?

Anna
I am 36 weeks and my doctor believes I may be starting early labor. He wants me to keep track of my contractions. However, I had a non stress test the other day and it picked up that I had 4 contractions within 30 minutes... I DIDNT FEEL A SINGLE ONE. Without judgement, can someone please explain to me how to tell the difference between my baby girl just pushing out hard on my stomach or if it's a contraction? Because the contractions that I know for sure is one, makes me belly feel the same way as it does when she's just pushing really hard. I'm smaller so it's hard for me to justify which is which.