Labor starting?

Ftm here, 39 weeks today. Up until now I haven't had ANY false labor pains and no BH that I'm aware of. I woke up this morning just feeling "off." My stomach was a little queasy, I was very tired, and haven't had much of an appetite all day. I laid down to take a nap and woke up to a gripping cramp that started at the top of my belly and radiated downward and through my back. It lasted about a minute. They say when you have a real contraction - you just know. And in that moment I DID "just know." After that, I haven't have any more that strong, but my belly has been tightening and mildly cramping off and on. What do I make of this?