Contractions only lasting through the night??

I've been getting some pretty painful but bearable contractions every couple days that last all night but as soon as the sun starts to come up they go away. I have tried everything to keep them coming but nothing works. This have been going on for 2 weeks and it's driving me crazy! I get no sleep, I rush around and clean the house and get everything ready to go to the hospital and then the contractions stop. They will be 5 minutes apart for an hour and then all of a sudden get sporadic for a bit and then become time-able again. I didn't have this problem with my first so I don't really know whats going on. It's like my body just changes it's mind or something. I'm really scared that this is happening because the baby is too big so nothing can progress. I told my Dr. this last week and she said she doesn't think thats why. Ugh what is going on?????