What to do...?

I been talkin to this boy joseph for five years and we recently started a relationship(like a month ago) but before we started our offical relationship, i had been talkin to this boy demetrius... i have a little bit of emotional feelings for demetruis but i love my boyfriend... a couple of days ago i was on the phone with demetrius and he told me he had fallin in love with me and i couldnt say anything in response... So what should i do?