I think I had contractions last night...

I'm only 31 weeks. My stomach didn't feel like it was getting hard, but I was definitely feeling some painful stomach cramp-like pain that started in my lower back. I only had three of them, and they were within an hour. Then they stopped. I'm not having any today. My next appointment is on Friday. Since I am not getting anymore of them should I wait, or call my doctor about it on Monday?