Did this guy ever care about me or was he using me the whole time?

I dated this guy in the navy for a few months. We met through a friend and we talked on the phone several times and really hit it off. So one day he came to visit me and when we first saw each other we hugged and kissed and there was so much emotion. we went out that day and he showed a lot of pda making it clear that we were together and I was his. He left that night and came back a few weeks later to stay for the week. Everything felt so natural between us and I really fell hard for him. I had with him a few times, which i regret doing now. We went to a party on a friday night, where apparently he got wasted after I left and had with a girl. He never told me about it but I could sense something was wrong when we would talk and he started acting cruel to me. So I ended it with him because I didn't know what else to do. I later found out why he was acting so weird. After I found out, I told him to leave me alone and he hasn't talked to me since. He got together with a girl 3 weeks after we broke up....why would he do this to me? Is she a rebound or did he really not care about me at all?