I'm in love with someone I can't have... but I can't get over him

This is a long story so brace yourselves... About a year ago, I began working on a show as Assistant Director (I'm a theatre major). I started to get to know one of the actors more and more; we spent almost every break during rehearsals chatting and I ended up catching some serious feelings for him. I learned soon, though, that he had recently started dating this girl and after my initial shock and anger I started trying to get over him. I figured that since my crush was fairly new I would be able to move on pretty quick. Boy was I wrong. We had rehearsal every day for a couple months (this was a huge Shakespeare production) so I saw him every day. And talked to him every day. Now he is fairly good-looking, not out of this world or anything but he dresses well and most of all his charisma and personality and humor are captivating. He is so easy to talk to and everything about his personality makes him so so attractive. I kept getting the feeling that he was flirting with me. He would make a point of talking to me and complimenting me and making sure I knew how much he liked being around me and even initiating playful touch as well. All of this made my heart flutter but I was so confused and a little guilty because he had a girlfriend I thought. Flash forward to the spring semester and we are not working on any shows together. I'm a little bummed because I wanted to spend more time with him but I thought "this could be good, I can get over him now." I'm assistant directing another show and I get a little bit of a crush on a guy in that show, so I'm thinking this whole thing with the other guy is over. Nope. My school sends a bunch of students to a theatre competition every year for various areas of theatre. I went this year for directing... and the one guy goes for acting. This competition is a week long stint of around 25 of us in close hotel rooms and spending all day every together in a convention center, competing or doing workshops or watching plays. It was really smooth and I got to get to know some people I hadn't known very well previously. All was well until the last night before we were scheduled to go home. One girl invited me and him and another girl to her hotel room to drink and watch a movie. So by the time the movie ended we were all a little tipsy and I had a bottle full of double vodka cranberries from earlier (the hotel was giving out free drinks). Me and him and the other girl were all standing outside her door chatting. It was around 11pm and the girl decided she was tired and went to bed. Everyone else was in bed. Me and the guy just look at each other for a moment and he says "I'm not tired, are you?" and was like "no I'm not" so we just walked around the hotel lobby, passing my bottle full of vodka back and forth, talking and getting more and more drunk and I was like oh no I'm not over him. He told me I was classically beautiful like Audrey Hepburn and he asked me if I wanted to continue the conversation in his hotel room (which he did share with a couple other guys so it wouldn't be just us, although they were asleep and there was an empty sitting room in the room). I was like "yeah sure" but I needed to go back and get my room key because I realized I had forgotten it in my room. So I go back to get my room key and the girl I was sharing a room with comes out and is like "can I join y'all?" and I reluctantly said ok because I couldn't think of a reason to tell her to leave us alone. So for about another hour the three of us just chilled out on the couches in the lobby, and then we all went back to our respective rooms around 2 ish. A week later we went to spring break and then quarantine hit and so I haven't seen him since. I started dating the guy from the other show but we broke up after a couple months. We talk less and less lately and sometimes I'll think I'm over him, but then I'll see something on social media or he'll show up in a dream and it'll all come flooding back. I can't get over him and I'm heartbroken and sad... Any advice for unrequited love?