Most Helpful Girl
Doesn't look like you have had very helpful advice so far.
Right I did the same as you about 4 months to my boyfriend. Strangely we got on really well, but there were some things in the relationship that I was just finding unacceptable eg. him continuing to talk to exes and putting me down all the time etc. I had enough and out of the blue broke up with him. I did it via email first because every time I spoke to him about anything emotional he would break down in tears, which in itself was manipulative. I got a reply back answering all the things I thought he had done wrong, and he apologized sort of, but he didn't really ask me to come back or suggest he would change so I moved on. Now don't get me wrong I went through the guilty phase and the regretting phase but it had to be done. I was unhappy in the relationship and it just wasn't moving forward.
Now you are going through the guilty regretting phase of the break up. You need to remind yourself why you broke up with him the first place, like you said you got fed up, why? What did he do?
You really need to consider whether trying to get him back will be beneficial to you, will he really change?
It seems a little odd that he won't even speak to you? If he really loved you, surely he would fight a little to get you back. I would definitely give him the letter, he needs to know why you left, otherwise you will always feel like you never got your side across. I mean what have you got to lose, when he isn't talking to you anyway.
Break ups are really hard, a lot of people think that the dumpers are always evil and bad people, but sometimes we're just the ones who had the balls to say this relationship is no longer healthy and not good for either party.
It may take a while for him to begin talking to you again, but he will get used to the idea and if he realizes he has done wrong he may even try to salvage things with you. Of course at that point you have to look at what you want.
Give him the letter :)