Had sex with my ex

I just couldn't help it. We were hanging out and I really wanted to. And it sucks because I'm kinda talking to a guy. I say kinda just because I'm in the stage of getting to know him. I'm not sure if he's interested in me 100% so my thought process is, "if he might be talking to other girls, I should talk to other guys" 
I just don't want to seem obsessed with this guy I'm getting to know so I'm keeping my options open until I know for sure what he wants.
My ex isn't one of those "guys" though even though we did have sex... He knows that we aren't getting back together. He called it "friends with benefits" even though I'm not sure id want to do it again.
I mean I'm single so I guess technically it's okay! But honestly I'm trying not to have sex anymore. But I couldn't help it.