Confused about contractions...

Ch

Hello ladies. I am currently 35 weeks and 3 days along. Getting close closer and closer! This is my first pregnancy. And I'm a little confused about contractions. I just saw my doctor two days ago. And she kind of tried to explained them, but pretty much said "You'll know when you have them"🤔 That isn't helpful lol. And the difference between BH and regular contractions.....I don't get it. So this morning I all of a sudden got a cramp in my pelvic area that kind of felt like period cramps. I thought maybe it was a BH, but it hurt and my doctor said BH contractions are painless? It was crampy feeling like that for 2 minutes. And then my belly starting feeling very, very tight. It still feels right now, 20 minutes later. Can anyone explain what is going on?