I cheated on the man i'm in love with...what do i do???

We've been dating a little over a year. i slept with another man one time and i told my boyfriend. he is pissed and says he hates me. calls me a whore and liar and all kinds of names. im still in love with my boyfriend and dont want to walk away. i dont know what to do? we've never had any serious fights or issues....this is the first one. any advice would be appreciated. im very desperate here. i dont know why i cheated. our relationship was so awesome! our sex life couldnt have been better....i dont know why i did it!!! please help