cheating

hmmm...when my boyfriend was away last week i stayed over at his mates house...and stuff happened between us. now i think its made me realise that i don't love my boyfriend...he doesn't make me feel appreciated or like my opinions are worth anything. i think i should break up with him, because its unfair to treat him like this...but i'd have to give him a reason and he seriously would kill the mate i cheated on him with, if he found out, and it would ruin so many different relationships because my best friend used to go out with the mate too, and the mate also has a girlfriend...its a huge mess.