Ex trying to contact me?

So me and my ex have been broken up for about 7 months. We completely stopped talking for two months, then briefly came back into contact, then completely stopped again. For the past two months, he's been periodically messaging me on Facebook, and after I respond, he doesn't. He recently did it again a few days ago. I don't know if I should ask him why he's been messaging me or if I should just leave it alone?
Ex trying to contact me?
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