38 wks and contractions??

I woke up at 2am this morning with major cramp like feeling which was totally strong. Tried to go to the bathroom but no dice. Then it kept happening about every 20 minutes. I thought it was tied to the too many scoops of Naturally Nutty that I ate last night after 9pm (I again had to sample each one). But it is now 3pm and it has not subsided - but also hasn't gotten any faster. I am having about 1 minute of a major cramp that doesn't go away no matter what I do and majorly hurts, goes away and comes back 15-20 minutes later. All day I felt like I was constipated(sorry TMI) but drank loads of water and ate fiberous (new word) foods. Is this contractions? I called the doctor and I'm going to go in tomorrow morning to get checked out if it continues but I have nothing else going on. I don't think I'll be hopping on the treadmill today! :(

I ran last night and it was a really good run, except by the end my lower back/top of my butt had started hurting and lasted into the night.

It was interesting trying to teach classes when one of these cramps came along and I wanted to yell out "MOTHER #$@#*(!!!!"