What to do when you break up with someone you love?

I'm only sixteen blah blah to young to love. Well I have been with this boy for three and a half years middle school and highschool. I love him very much and I thought he loved me but the reason I broke up with him is I don't think he is loyal because he has cheated on me once and swore not to do it again but also lies to me alot. I can't trust him so I wanted to end it. I'm a mess though because I love him and I'm having second thoughts maybe I shouldn't have. HELP?