Close friend, always been a bit of a spark between us but nothing has ever happened. We've both been in relationships for most of the time we've known each other, I am now single and he isn't. We slept together two weeks ago, I feel absolutely dreadful. He's been sweet to me ever since but he isn't going to leave his gf - I told him we can't speak anymore. I feel horrible for what I've done but also realised my feelings go way beyond friendship. I know the fairest thing to do is get out his life and stay out, and I know what I've done to his poor gf is horrid but I just feel so sad.