Ft, sounds a lot like mine, never got that regular until I got to hospital and was 5cm on arrival. Had some 4 mins apart then one would be 15 mins. Took a while to persuade triage to let me in cos of that! think the car journey sped them up, worst 8 min ride ever!
Only way I could handle them was on all fours, after 24 hrs of that I was knackered so if you can grab any sleep do.
Good luck! X