Mine has lasted for almost 40 min
I sometimes get Braxton hicks contractions where my tummy tightens up and gets lower back cramps, and sometimes when my tummy tightens it puts a little discomfort to my belly, but it goes away within minutes or so!
I do in the evening sometimes when my belly is extra full with food on to of the baby. I think it's just skin/muscles etc stretching. It feels like that to me anyway.