You can tell him that you need some "me" time. There is nothing wrong with that. Remind him that he fell in love with the person you are and you need to take care of yourself. The same way he needs time to take care of himself as well. Explain that this will allow you two to have more to talk about when you do talk as well as allow you both to move forward in your lives so there will be something substantial for the both of you in the future. Try to phrase it as a good thing, not as a negative towards him or your relationship. Just that you want to make sure you don't fall out of love with yourself and resent things because you lost you along the way.
And make sure he knows that it isn't a total break. Cut daily phone calls to every other day. Or every third day or something. Make sure you schedule time for each other too, not just the phone calls and the personal space. Make dates with him. Plan to go out with him. Basically, try to organize your life and make sure he feels that he is a big part of it, but that you need to make sure all parts are handled.
Good luck!
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