I have just been through an extended night of it. Seems to have gone away now. This did not happen with my first child so it has taken me by surprise. (I have technically another 4 weeks to go.)
I had contractions every 10-12 minutes for a few hours -- then they slowed down to once an hour or once every half hour.
It's so frustrating not knowing whether it's the real thing or not! Especially when you have an older child who will have to be taken elsewhere and you don't want to get her up in the middle of the night.
Now I'm supposed to do nothing all day to keep it slow...