I left him. Did I make a mistake?

Hey, ladies today I need a little reassurance or some personal opinions on a situation I'm in. So I've hated this dating app for maybe 2 years now and I've met a few guys from it but nothing that ever turned serious. I only really hang out with 1 girlfriend so I figured maybe instead of trying to date I could meet some friends from the app. I found this 1 cute guy who said in his profile he was only looking for friends so I messaged him saying "platonic friends would be awesome". Everything actually turned out great. 1 day he asked if I had a bf I said no and asked if he had a gf. He said it's complicated she lives long distance so they have an open relationship. Instantly I felt a little uncomfortable with a guy talking on the phone with me all night who has a gf but I thought we're only friends so I'm worrying for nothing. So a month passes and we're two peas in a pod. We talked every night until 5am and hung out once or twice a week. That's when the constant complaining about his gf began and the "I need someone more mature" Then 1 night while we watched movies at his house he kissed me. I forgot about everything and kissed him back. It just felt right but I stopped us from going any further. Time passes and we continously have make out sessions in his room. I was extremely attracted to him but still my conscience said don't have sex he has a gf. Another month passes we get into our first arguement. I was getting tired of him treating me like his fill in gf. I was still ok with us kissing from time to time though. Then he wanted to stop kissing and revealed he was starting to have feelings for me and the kissing made things hard. So we stopped. Then almost a month later I txted him 1 day and got no reply. By the second day I was worried so went to his house to check on him. when I got there his phone battery was broken and he was expecting a new phone in a few days. We were hanging out in his room...and then we had sex. I knew I was being stupid but I was falling for him. We had such a deep connection I'd never had from the start. Guilt, Possession, and insecurities were plaguing my mind. " I know he's not gonna leave his gf, I shouldn't want him to leave her that's terrible...but he complains about her and he'd be happier with me" I ended our "friendship" 2 days ago. I was being way too obsessed with how a boy felt about me when I have Clinicals at a hospital in 2 weeks. He said he understood and then texted me the next day with "..." I replied with "what's wrong" because I still care and he didn't reply. I miss him loads. Do you guys think I made the right decision going with my brain instead of my heart???