What is wrong with me.?

So I've been on and off with this guy, a fuck boy for 3 years. Your typical player. Recently I found out that he was in a ongoing relationship with a 15 year old girl. He is 24. I found out because she came to me and asked me who I was. They have had sex. I told her the truth about me. I might add this isn't the first time he's been involved with a minor. We clearly aren't talking anymore because parents got involved and in a huge mess. Just for some reason I still have feelings for him and it hurts not to talk to him. I don't understand how I can have feelings for a person like this. Just want thoughts about this.