Is this a contraction/Braxton hicks or something else??

29 weeks. It's only on the lower left side of my belly but it's a tightening pain and then releases. I've had two in the past ten minutes. The first lasted a couple minutes. The second one only lasted about 45 seconds. This is my first and I don't know what they feel like. I assumed a contraction would be the whole abdomen in pain not just the left side but I really don't know. I know that sounds dumb, I've had them explained to me but I still don't know.