Lower abdominal cramping - braxton hicks or preterm labor?

I had this painful (little bit stronger than period cramps) in just my lower abdominal region. Like where I would have period cramps and the pain radiated into the top of my groin.

Currently laying down on my side to see if it goes away. Could this be Braxton Hicks or preterm labor? FTM and just unsure. Pain lasted for about a minute or two but has happened a few times this hour on my walk. Not sure if I should call advice nurse, rest or get checked out? Currently 31 weeks.