I think i had pre-labour from the 37 week mark with DS2 & DD, they were cramps and twinges here the there but i was awake at 3am when the real thing started with DD and the feeling (it wasn't pain then) was completely different. I'd explain it as a thick feeling across my lower belly. DS2 was different, the pre-labour was similar but the real thing started with my waters breaking and no other feelings at all at the time.