Labor?

Since midnight I've been having a tightening wave in my belly, they are about 15-20 mins apart. They're not painful and last about 20 seconds. I tried drinking water and getting up walking around. Still happened. I'm a FTM, 38w 3d, last week I was 75% effaced and 1 cm dilated. I haven't lost my plug yet. Should I go to the hospital to get checked out or should I wait for my doctors appointment that's tomorrow morning?