This thread is enlightening... thank you OP! Actually this sounds quite similar to me. Although at 35 weeks my waters broke - tho there was no "gush" just a light trickle. An hour later I started experiencing some movement and what felt like very mild period pain. Half an hour later I was in full blown labour with contractions a minute long, three mins apart. I was in transition in the car on the way to the hospital (I literally had to cross my legs). I was already 10cm and less than 15 mins after getting there delivered a breech bub with three pushes. 1hr and fifteen mins from first hint of contraction (or anything really) to crowning.
The only explanation I can think is that I was having silent contractions in the days leading up to the birth. Am preggo now (12 weeks) and my midwife said there are other signs to look out for... not sure what these are yet, but definitely going to do some more research.
Thanks again for the lead!! Am so nervous hubby is going to have to deliver this bub on the kitchen floor with my toddler looking on 8-/