Mine were each different, with ds1 it was all in my back, like a vice being pushed onto my back just below hip level, but not on the stomach, incredible painful pressure, that could only be relieved by someone pressing on a different part of my back lower down. felt fairly constant coming and going very close together for about 20 hours!
with dd it was more like a wave of pressure, starting low down and then rising up and getting more painful as it rose up to the top of the tummy til it felt like no more pressure could be added, belt tightening is a good analogy, the pain was coming and going for about 5 days, but then suddenly got much worse and then was all over in 2.5 hours.
with ds2 it was like a stitch, or trapped nerve type feeling, in between it was fine, was even typing on mumsnet between them, in fact I did not think it was labour to start with! Then suddenly got much worse as it was a fairly constant trapped nerve feeling but finished within 1.5hours, so manageable.
I think every labour is different and period pain is common in the build up to labour, but how it goes from there is an unknown as everyone is different.