Is my ex flirting with me?

So my "ex" and I broke up a little over a month ago. We dated unofficially for 4 months and then a huge misunderstanding happened and it kinda ruined things temporarily. A few weeks later we started talking again (about a month ago now) and we've been talking every single day, just as much as we used to. In the last 3 days I think he's been flirting pretty heavily with me, but I could be wrong. Last night he made an ass joke and I was like "yeah I do have one" and he goes "Nice bum" and I was like lol where ya from and he goes "(where he's from) wanna fuck it?". The nice before he asked ME if I was flirting with him (I kinda was). I sent him a stupid Santa bitmoji and he goes "you still tryna sit on my lap???". Like, I just feel like these aren't strictly friendly conversations anymore but I could be wrong. We Snapchat all day and text at night. My birthday was last week and he was the first one to wish me a hbd (he stayed up even though he had to get up at 6am). Should I ask him what the deal is or just flirt back and see what happens?? Or is this not flirting at all? I'm always so scared of misinterpreting signals, lol. We've hung out once since the "break up" (we go to different colleges) and it went well.