will you help me?

there's this yaoi/shounen-ai manga that i've read years ago that i've forgotten the name of it. but i do know that somewhere in the story it goes like this: the main character has an affair with this guy he used to date, but the guy is married and everything, but the married dude won't stop his affair saying that he needs the main character or something like that. anyway, this third guy comes into the picture and sleeps with the main character. little by little, the main falls for the third, when the second finds out, he thinks he could win main back by sleeping with him, even though main denies it...

and that is where i left off. any ideas which manga i'm talking about?