Preterm labor: what were your symptoms?

I'm getting a little worried. I'm 33 weeks. I know all of the symptoms I'm about to list are also common third trimester symptoms, but I also experienced them before my water broke with my first so I'm curious.
It started Saturday with an all over achy and exhausted feeling. I honestly thought I was unlucky and coming down with the flu. Then Sunday & yesterday I was contracting on and off all day. Yesterday I had about 50 contractions from 11am-11pm. I also lost the largest piece of my mucus plug thus far. 
Anybody else having/had these symptoms and it wasn't preterm labor? If it WAS how long after these symptoms began did you go into labor? I know every pregnancy/woman is different, but I'm just curious!