I’m so confused by at guys mixed signals at the gym

I’ve been going to the gym for a few months and I’ve noticed this cute guy who’s been obviously staring at for for a while now. One day i noticed that he just happened to be in every area of the gym that I was in so I decided to be a brave girl and give a smile/ say ‘hi.’ Nothing much came out out it but I noticed the days/weeks after that simple interaction he would be more obvious with his staring and would somehow find ways to work out out near me. To me, i figured it was an awkward attempt at flirting so I would just give a smile back here and there.
So one day I bring my friend w me to workout and I point out the cute guy to them and ends up that my friend knows who the cute guy is! Apparently they had mutual friends back in high school. My friend shows me his ig and I find out that he has a whole ass gf of 2 years!! So now I feel like an idiot who completely read the signs wrong. Now here’s where I’m confused. The sec I find out about his relationship I back off completely and stop w the subtle flirting/acknowledgment of him. But now I’ve been noticing how he’s working extra hard to get my attention: staring, working out where I am(like he has literally found a way to work out next to me while I was all the way across the gym tucked in the corner), etc. so now I’m madly confused bc I get the feeling that he wants me to notice him even though he has a gf (keep in mind that he doesn’t know that I know about him). I just need to a place to vent and would like to hear anyones else’s perspective or opinion. I don’t want to engage or instigate anything with him but I’m just so confused on what his objective is for his behavior.