HiCustomer Thank you for asking your question on JustAnswer. By the way, it would help us to know:
-Did the two of you live together?
-Has he been going through something in his life lately?
-Could you explain your situation a little more?Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
It may be that he is dealing with some kind of depression and doesn't know how to handle it. Since you said that things between the two of you have been really good then I can only assume that he isn't happy with the other aspects of his life. I would stick it out with him and tell him that you are concerned for him and that you think he may be depressed maybe if he hears the words he will check with his doctor to make sure that this isn't the case. It's important to at least keep contact and communication open in case he needs someone to talk to and confide in. He may not have wanted to burden you with his problems but if he is depressed it isn't a good idea for him to be alone. Maybe talk to his friends and ask them if they feel he may be depressed about something.
Maybe family members may be able to tell you what is going on with him lately, it sounds like he didn't give you much reason for him needing time alone besides the fact that the two of you may have been moving too fast, reassure him that you are not wanting to rush down the isle. I really don't think that is it because you lived together for two years nothing gets more committal than that. I think he is struggling within himself and don;t know quite how to deal with that because he hasn't felt this way before.
Give him until until Tuesday so that he doesn't feel overwhelmed with everything this way he will have had a few days to comtemplate about everything and he may be able to give you more answers if you ask him all of your questions at once it may frustrate him and push him further away.