Woke up this morning... *Update

With horribly intense contractions. My back is killing me, and I've had constant menstrual like cramps. I decided to get up, drink a bottle of water and eat something before I started timing them, and they're coming every 3 minutes and lasting about a minute and ten seconds each. I can feel it getting tighter and tighter like I'm about to pop, and it wraps around my back and causes more cramping. I tried walking around to see if that helped, changing positions, drinking more water, and they're still coming like clockwork. I had this happen last Friday, almost identical, and it was nothing. Never progressed past 1cm. I was 1cm at my 38 week apt yesterday, but she did a membrane sweep, so I'm so unsure if I should head in or not. I really don't want to be sent home again, especially if I can labor at home for a little longer anyway. Has anyone experienced this? When should I head in?