Sex and contractions!

So last night (after sex) I went to sleep feeling rather crampy throughout my lower abdomen, hips and inner thighs. I woke up at 1 am contracting, cramping, and experiencing lower back pain. I tried to sleep through it, but couldn't. I decided to time them (they lasted almost 3 hours and were consistently below 4 minutes apart for the first hour of that). Finally they eased up and I was able to go back to sleep. I'm 36 weeks and some change. Anybody have similar experiences? I am so excited for baby to get here, but goodness was that pesky.