Should i ask whats going on?

So as a few of you know, i met a guy around a month ago. Things seemed to be going really good, he was always contacting me. If anything he was the one who seemed to be more into it than i was. Or at least just as much anyway.
Well since sunday he has seemed unusually distant. It is very noticeable.
Before he was constantly asking me to hang out, he hasnt asked me once since last friday. He didnt even call, text or message me one of the days this week which is SO not like him.
Today is the first day he really text me out the blue while i was at work. It was quite a cheeky text.. Asking if he beeped going through the doors would i be the one to search him.. lol

He hasnt called me though at all. Ugh. I dont get what the hell could have happened for him to back off like he did.
Now, the question is, should i mention this to him? Or act like everythings okay?
We werent particularly close we could talk about anything and everything. But i felt like we were getting pretty close before this past weekend.
I was thinking about just stating i had noticed he was distant (he must obviously know he is being) and asking why. Or just play it cool and be distance back?

Im not sure what the best thing to do would be, what would you do? In order to keep him interested that is.

You can ask him - just make sure you do it in person, and playfully. Make a joke out of it.

Then it's on him - you'll learn a lot about him by the way he answers. If he brushes it off and doesn't answer, he clearly doesn't get it (or is hiding something). If he says "you haven't contacted me either!", he was testing you. And so on.