1st Baby 33 weeks and Cramps

Hey Ladies,
So this is my first baby, and I am trying not to over-react and be a complete worry-wart over here.
Yesterday, I started to get cramping. It felt like period pain and wrapped around to my back. It was pretty uncomfortable. And it last from 1:30pm-3:05pm. 
It happened again 8:30-9:15pm
And then again this morning.
It's not happening constantly. And obviously it's stil pretty early. So I am wondering if I should be concerned? Or if this is all part of the 3rd trimester?