Hi, I'd like to help you with your question.
From what you said, it sounds like you may want to go out to see your boyfriend anyway. It is hard to determine whether or not he is depressed again, or there is a problem in the relationship.
The fact that he keeps pushing you away can mean many things. One, he is hurt by you leaving and is rejecting you in response, two, he is really depressed and doesn't want to let you in because of that, and three, he doesn't feel he want to stay in the relationship. I know, that is not something anyone wants to hear. But considering it as a possibility is smart because you don't want to be thrown if that is what is actually happening.
The only way you are going to know for sure is to see him in person. You could always just wait and see what he does, but based on his behavior so far it's not likely that he will keep in contact.
Are there any mutual friends you can call who live near your boyfriend? Maybe they could check on him and give you an idea of what is going on before you go out there. Any bit of information is going to help you prepare before you see him.
If you go out to see him, let him know you care about him and want to help, even if it is just as a friend. Be gentle and non confrontational. Give him space if you feel he needs it. Enlist help from friends to try and get him help, if needed. If he still wants the relationship, it will work out.
I hope this helped you,
You can only let him know what you see and tell him you are concerned. Let him know what you have told me and see how he responds. As you may know, you can only force treatment on him if he is suicidal or homicidal with a plan so you won't be able to get him help unless he is willing. But you can try talking with him the best you can.
Other than that, there is no certain thing you can say or do to make him see what he is doing. He needs to gain the insight on his own. But you can be there for him as much as he will allow. That is being a good friend to him and that will mean a lot.