Braxton Hicks or contractions?

I'm 39 weeks and lost my mucus plug. The same night I started having contractions that seemed intense and we're starting at about 30 minutes apart and got closer and closer over the next six hours. I got up to shower and get ready to call my doctor. The contractions then started getting farther and farther apart. They started up again and we're getting close but now I haven't had one for 45 minutes. What is going on?