What do you do when you're on the receiving end of the silent treatment?

What you're doing is right. You are giving him space to think about it. Problem is, he doesn't know any other way to deal with what he feels. What probably happened is that when he was a child he learned that by expressing his feelings, the result is undesirable. maybe he got punished, maybe he didn'r get the response he was hoping for. So he decided to bottle up the emotions. What once was a conscious decision is now an automatic response. Whenever something upsets him, he retreats. Unfortunately, this behavior is always a problem for the relationship because the other person (you) feels shut off. Naturally, you'd like to hear about why he is upset, you'd like him to open up so that you can work it out together. Have you tried to tell him that? How much you wish he could just sit down with you and talk about it? Everybody wants to be heard, to be understood, and your boyfriend is not the exception. He just doesn't know how to do it. He is embarred and scared that by doing that he will lose something, like maybe your respect, or maybe he will be appear weak..He needs to be encouraged. Now what he is doing, still not contacting you on day 3 is making you angry and confused, but he is most probably just as confused and upset as you are. you need to talk to him. gently, kindly. especially because you say he is perfect in every other way. he needs to be sure, to trust that you can deal with it no matter what it is that bothers him this much. since he is worth it, you need to try and make him see that you will continue to care no matter what he has to say. and make sure to explain to him that this is how relationships work. good luck