Back pain or back labor?

Hey mamas! So I am currently pregnant with baby #2, I have been having really bad back pain off and on since around 6/7 PM yesterday, it’s pretty bad when it starts and doesn’t last long, it’s been off and on all day. I notice it is worse when I’m having Braxton hicks or when she moves. My baby has been measuring substantially ahead my whole pregnancy and was about 5.5 pounds when I went last week, do you think it’s just back pain or back labor?