Confused and depressed

I have been in relationship with my bf for almost 2 years. but before i knew my bf i was having a contact with this guy A which i have fallen for him but unfortunately he was just treating me as a friend and he was a very good friend so i moved on and accept my bf proposal that time. when i moved in with my fb we stop contacting each other to avoid problems between me and my bf. Now im no more living with my bf since i have moved to the other town due to my work. once i have moved from my bf place we starts to talk to each other again. Now A is in love with me but he knows that he should'nt since i have bf. Nowadays I can feel that i have feelings for A again but I love my bf too. My bf have been such a caring guy towards me and I cant break his heart. A knows that I couldnt accept his love and he understands but i feel so depressed and confused. I dont know what should i do :(