When I was 19, I started to see this guy I had know since I started high school. Everyone we knew kept telling me that he really likes me, even my sister of whom i am very close with. She even pointed out that he was a little hurt of my choice of boyfriend a year before. He told me that he was going in to the Navy in two months. I was fine with that and i figured we could be together till then and i would wait for him after that. After a month of seeing each other, he confessed to me that he really didn't want a relationship right now and that he found a love interest that he had been looking for and sort of wanted to see her. I said ok and then a few days later he were "together" again and he was saying that I was his girl. Our relationship continued like that for a little while. The beginning of the last month he was to be here he started to not return my calls or my messages on Myspace. This lasted for two weeks until he one day showed up on my doorstep like he use to. He sat for a bit with me like he use to, except he was unusually quiet, and then he got up and left. I never saw or heard from him again. Did I mention that I was passionately in love with him?
i learned two things from this experience. 1) People who are leaving for long periods of time and are bothered by it are very unpredictable. 2) not all men are worth that kind of trouble.
There are two sides to every relationship. One person cannot be to blame for everything that goes on. I do not think you are to blame, I feel that he is because he needed to be more open with you if he knew he felt that way, or at least handled it better. If you feel that he is worth this trouble and have tried to apologize and tell him that you are sorry, tried everything in your current power, and he still ignores you, then there is nothing more that can be done. The note idea from Beagle is a good idea. If he is so privet that he would act that way, then a letter would be your best bet, but try not to go through his friends, send it to him through the mail if you can. If doesn't reply to you then, then I guess you have your answer, and I'm sorry for that. If he does, then it would be a good idea for the two of you to discuss his boundaries and anything else relating to them and possibly redefine your friendship. But like Beagle said, this could be a red flag and you really need to be prepared for the fact that this may not work out.
Also keep in mind that people have a tendency to over react to the small things when they want out of a relationship. All of this just might be telling you that he might be using this excuse to get you out of his life, re leaving him of the burden of breaking up, and making you feel that it was your fault. This thought may be a possibility, but it also could be me over analyzing things. I guess you can ask around and see if this is normal for him to treat people like that for coming over unannounced. Don't take this thought to heart though. Find the truth.