Whyd he do this *10 points*?

Long story short, I can't date till Im 18. I have made out with this guy A since April, then 2 weeks ago he said he loved me and wanted me to be his girl. Then 2 days after that, he went on a date with another girl. I got upset, and made out with this guy Brent that I've always liked. A got mad when he found out. I sent him a message apologizing, and telling him I loved him still, but he didnt respond. Then we had an IM conversation and I said "Hey, you don't like me anymore, right" a minute later he signed off. Why'd he do that?