Mama, this timing mismatch is something your OB really needs to sort out properly, please bring this up sa next check-up, or call them now if you're worried. The difference between LMP at ultrasound dates can happen, pero kailangan nila i-clarify kung alin ang accurate para ma-monitor mo nang tama, lalo na with the regular tightening you're feeling. That said, Braxton Hicks (practice contractions) around mid-pregnancy onwards ay normal, pero palaging better safe than sorry pag may doubt.