Relationship advice, please?

I have a boyfriend, it would be 10 months tomorrow, but I don't know what to do... I'm in 10th grade, and this guy, lets call him A, has liked me on and off since 6th grade, and the gut I'm dating, lets call him K, I love with all my heart, but I don't have feelings for anymore.

Me and A have been hanging out everyday for a week now, I realized I never stopped likeing him, I just pushed my feelings aside, I stated letting them out, I told him how I felt, he liked me just as much, he never asked me out though- and I think it's because hes been dating this chick for a few days (he never even told me, and since he didn't, he cheated because we have done things).

I love K with all my heart, but I don't get butterflys for him, I don't feel an attraction to him anymore, unlike I do with A, but A just wants to be friends now. I don't wanna be there for him when he gets out of his relationship just as a rebound.

Should I let K go? and focus on other guys, like A? or do I let both of them go? Because I don't feel for K, and A played me?... Help, please?