Is my work crush....flirting with me?

sooooo I started this job and he started a couple of days after me. As soon as I saw him I thought he was cute but we didn’t talk for a while. I’m assuming he’s just as shy as I am. Fast forward a week or two and now that we’ve been working together for a bit, he’s more comfortable. Always teasing me and singling me out from everybody else. Don’t get me wrong, he’s friendly with everyone....but me, just a little more...? The banter between us is great! You could say I’m crushing.....But another big detail, he has a girlfriend. She lives out of town. He doesn’t mention her often and the only reason I know he’s in a relationship is because I’ve heard him briefly talking about it to someone else. He’s never directly mentioned her to me. (Not that he needs to..) It’s hard for me to tell if he’s flirting or not and I don’t wanna be that person but I low key think he is...He doesn’t compliment me or touch me in flirty ways. He’s just very playful with me and it confuses me cause I’m the only one he’s like that too... I sure as hell don’t flirt with him... I’m not one to initiate things and especially not things like that. I’m only responsive to others...maybe he’s comfortable around me or just friendly! And that’s that.