Is it bad to miss him

I don’t want to say I wasted 5 months of my life not even dating a guy because i thought I was having the best thing in life and though god gave me what I was asking for.. but I now I don’t know what to think.. I’m 17 and he was 20 using me just for sex for those 5 months.. I disrespected my parents by letting him stay over and going and staying at his place. I did everything for him and his family I followed them to there stupid little parties so I make sure that him and his cousin were always safe.. but in the end his cousin slapped me in the face and he wouldn’t do anything about it.. I’m sorry but it’s not okay for a guy to hit a girl anytime.. but I was still doing what get to make them happy they were my best friends.. come to find out he gets in a relationship a week after we found out we were never dating and gets engaged to her after only knowing her for a month.. I can’t help but still miss him how can I get over this so I can focus on my self