Cramping at almost 35 weeks ... advise please girls!!!!!

Lois

So over the last couple of days I've been having period pain type cramps on and off. Today noticed them the most, they can last anything from 2 minutes-20 minutes but theres no pattern. I get them the most when I stand up from sitting. It's painful but not agony and I don't seem to tighten at the same time.

What could this be??? Any ideas? Thanks x