Yes I can completely see what you have no clue about what to think! He is one confused guy and is sending out totally opposite messages. So, basically it DOES sound like you two are at that point where you are going to move forward together in a more committed way (he was thinking of proposing) OR possibly go your separate ways. It really sounds like he is at that crossroads where he is trying to decide if he in fact does want to become more committed or if he wants to perhaps just break up. I only say this as he said he wants to only be responsible for himself, pursue his career goals and so on.
Men often have these kinds of thoughts come up when they are faced with the idea of marriage, etc. He is assessing where he is in his life as an individual, what he wants for himself, etc. This is what he is doing. Getting space from you so he can gain more clarity for himself. It is okay for him to do this of course, but the way he had gone about this is not okay at all!
And again is a red flag to you. I understand that you just want things to go back to how they were, when you were happy etc. And perhaps they will...only time will tell.
I don't think it sounds like he has completely decided, but that he needs time to figure out what he wants. When you get upset, this bothers him as he wants to have this time to think about himself without having to worry about how it will affect you. That is being selfish and yes immature, but at the same time it's the only way he probably feels that he can get the necessary space and distance he needs to get clear.
I would let him know that while you are not happy about the way he has gone about this, that you of course will give him this space so he can figure out what is going on with himself.
And I encourage you to also use this time, to figure out exactly what you want as well, either with him or independent of him. There is a chance he will not want to get back together and you need to be prepared for that possibility.
I know it's tough, but in the long run, you are going to want a man who fully chooses to be there with you. Not someone who is uncertain and runs away when he gets scared or unsure. Keep that in mind for yourself. It's also important to continue seeing your friends, exercising, etc. keep doing things to stay active, so you don't get too absorbed by what he is doing.
You can also suggest to him that the two of you see a couples counselor to determine what is going on and how to get through this uncertain time. The main thing is to give him this time and space to just be himself and come to his own conclusions. I would really try to not contact him and just use this time to focus on yourself. It will be okay however things turn out, as much as you may not believe that at this time. Please let me know if there is anything more I can do to help you. Please keep in touch and all the best to you. Also, please rate my service today as I want to be sure you are happy with my help. Thank you!