Freaking out. What am I feeling?

Amanda
I don't wanna call my on call doc because I know right away she will send me to l&d they always do. 
My lower back is like cramping? Major pain the it like trickles to my stomach and its tight and sharp. Then it will go away and I will feel full achy period pains. I haven't tried timing it because I can't really tell when it stops or ends. Someone who isn't a first time mom, is this contractions? Happened after sex. I'm 36 weeks today.