Well I "thought" I was having BH starting around 20 weeks and the dr said it was normal even that early. However, as we all know, it wasn't BH but real contractions that caused cervix changes. I was told BH was a while tummy tightening that was irregular but that real contractions were stronger, reach around to your back, and are timeable. I don't think I have had BH with either pregnancy based on that. Mine are always low and wrap around my back.
Yep, I tend to get them at night or at least that's when I notice them the most. It just feel like my belly is getting really tight and when I feel it it's hard. Sometimes I don't feel them, sometimes I do. I think you have them more with each kid b/c I don't remember them much even with my second.