This is what happened to me!
Except my pre-labours stretched over about 2-3 weeks.
When the BH were 10minutely for 8 hours then 5 minutely then i called the hospital.
They werent severly painful at that stage though (so dont judge on pain) just uncomfy like i couldnt find the right spot to lay in - the back pain and period pain was there!

Fingers crossed it may be time soon!