I want to tell him I love him but dammit he makes it so hard how do i do it?

Okay so there's this guy, Nathan, he stares at me everyday he once told me in a note that he liked me but i didn't like him that way until he came up to me a few minutes ago and kissed me. After that kiss, he just walked away, looking back once and smiling at me. But then there's another guy I like and I've liked him for so long and just dropping him like a hot potato feels like a betrayal, what do i do now?