My boyfriend has feeling for my best friend

Hi all. I am so frustrated and hope that some of you could just help me clear my head and understand what I already know but somehow have no guts to move on. I am 31 , a journalist. I am dating with my boyfriend for about 14 months. A couple of months ago while he was very drunk (as usual when he goes out) we had a fight, I left early and in the morning he sent a message on linkedin to my bestfriedn that he would like to **** her (not with this words of course, but this was the message). I was devastated and stop the communication for a week. He was calling, senting messages, coming on my door, senting gifts, dinner and so on and so on . I finally agree to met him in a bar and here what he has to say. He said that this thing with my friend was some crazy delusive fixation, something that it is not real, that he finds her attractive but nothing really special. Somehow I forgave him. I had a lot of thing going on at the time, my mother commited a suicide, so I was just not ready to leave the relationship. Of course, my self-esteem was ruined and took a several month to begin to restore...I had terrible times sitting with my bestfriend without asking myself what does she has, that I don't and so on and so on...He wanted to apologize to her and after 3 month I let him do it and invited him together with us both on a drink. Last week he had a birthday and he told me to invite all the friend I want. He even mentioned her. I invited her. She came, everything was normal, we use to go out even before the birthday so it was not really a big deal for me. Than my friend told me that he asked her on the birthday party to give him his email so that he can sent her an "essey, a letter" where he is apologizing. I went crazy. I asked him and he said that it is nothing really special, that he wanted to do it so we can all go on, that this letter was more his monologue that a letter for her. I stop there and later I checked his lap top and find the letter. He even said (before this) that I can see the letter. He was basically telling her that he had strong and passionate feeling about her and that hefelt instinctive attraction and so on ... I just cant even put all that here it hurts me to check the letter again. That he does not know here, but yet he felt that. That he has the same feelings for me and her and that he is suffering from ,,emotional bilateral attraction conflict" ... I mean what the hell! the letter is not finished btw...I can not even imagine that he will ever sent this and even show that to me! So tell me that I ll be stupid to by this whole apologizing thing..he is only senting me messages cause i amlost block him everywhere, that he loves me so deeply, so much, so of everything, that he want children, marriage and so on that he never felt anything similar to another human being...But I just feel that this is not worth the trust and hate him for the emotions that he is making me feel about my best friend.