I'm having contractions?

Lindsay • Baby #4 on the way!
I'm 28w4d and have been having contractions like crazy for the past week. This is my third baby. I had Braxton hicks with my others, but these are so much stronger and hurt in my back and everywhere. They last about 45 seconds. I see dr on Wed and will bring them up. Just didn't know if this was common with third babies.