Mixed signals from co-worker

There's this guy I used to work with that I was totally crazy about. I thought about him all the time and when we had shifts together I didn't want to go home because I loved talking to him so much. First of all, he's extremely attractive and athletic. Second, he's really smart and funny. Third, he always liked cracking jokes with me and it felt like he tried to be around me as much as possible. He's honestly the guy that comes into my mind when I think of an ideal partner.The thing is, he's straight as far as I know and he has a girlfriend that he really likes. We don't work together anymore and I just have one class with him at school, and in school he doesn't talk to me that much.Still, I always got a vibe from him. He always told me how likeable I was and it seemed like he complimented my looks a few times. Like one time there was this shirt that said "I'm adorable" and I joked that I should buy it and he said "it would be accurate," but kind of joking maybe? Another time I told him I liked his eyes and he couldn't stop smiling for like five minutes after that. I also noticed that he mirrored my mannerisms when he was around me, or maybe we just acted in similar ways. Like when he was around me he was always awkwardly tapping his fingers or doing some weird breathing thing.I think I'm just thinking wishfully though. He acts completely straight (the only questionable things are some of his clothes and earrings), and when asked him about himself he seemed to really enjoy the conversion, but when I started flirting subtly I always got a cold response. Plus nowadays he never talks to me, and I never catch him looking at me like I look at him. He's still nice when I approach him, but if he's bummed out to not be seeing me as much anymore, he's not showing it. I should probably just get over it, but it's easier said than done.