I have scored the most perfect Prince Charming ever! The first couple months went great (it was all like you said - HE did everything! Decided for us to become exclusive, even started talking about marriage within the first month of dating) but as with all my relationships - a couple months later (about the 10 month point for this one) and the infatuation phase runs out. I know you say that backing off and giving him space will make him come back on his own and return as someone that wants you to be exclusive with him. But in my situation we're already exclusive! And he's still pulled back! Is there any advice for this? Is this normal?
My heart goes out to you now because obviously you're hurt and confused.
Even though he asked to be exclusive, is it possible that he's come to take you for granted?
In other words, have you given him a reason to take you for granted? Have you ever broken plans with your friends to be with him? Do you call him or text him often? (I don't care if you're a man or a woman; too-frequent contact is a romance killer.) Are you doing too much for him? Making his dinner all the time, picking up his dry cleaning, returning his library books?
If so, you're not making yourself indispensible. You're smothering him.
If this is the case, please do yourself a favor and take a step back. Start filling your time with friends. Go out for drinks for colleagues. Let him be the adult he is and take care of his own laundry, meals, etc. Let him do some things for you. Men like to do things for women. They enjoy giving things to women. If you've taken those particular life's pleasures from him, please stop.
If you back off for a while, and he steps forward again, remember this: Being an exclusive couple is great, but your boyfriend was attracted to you because of YOU-- who you are, what you do, how you think, what makes you laugh, and so on. If you allow yourself to be half of a couple instead of a full person in a dynamic, loving relationship, you lose yourself.
And he loses you,
Without a complete picture of your relationship, my best suggestion is to return to being the full woman the man fell in love with; if you have any preconceived notions about how a full-time girlfriend is to behave (aside from kindly, honestly, and faithfully), please drop them.
Be the girl you used to be.