The guy I like likes someone else?

I was getting on really well with this guy and i had been going to his house everyday and the last day I went I had sex with him, I had done it before but he hadn't so I thought that he would like me more and I only did it because I thought we were going to start going out cause we text loads, then I saw him at a friends BBQ and he was acting really weird and so I text him after we left asking what's happening with us and he said I'm really sorry I still like Millie (a girl he briefly dated before) and we've started texting loads, you can do better than me anyway. And it was just over like that! I don't want it to be over and now everyone found out we had sex and it looks really bad because were not seeing each other and it hurts so much I really liked him and now I found out he didn't care at all. Does this mean it's definitely over? His friend told me he was 90% me and 10% Millie so why has he chosen her?