Not baby kicks.. is it my uterus

Okay so this might sound kind of dumb but . I’m pregnant . And I just notice this pulse in my lower stomach . I know it’s not my baby kicks because it was continuously for a good few minutes with the same type of Rhythm. Oh I’m 34 weeks btw so I definitely know it’s not the kicks. Is it like my uterus and would anyone happen to know why it does that.