It sounds like the fires are cooling. Not all couples experience this, but the majority do. Many people are surprised when the new, exciting, alls-right-with-the-world feelings starts to wear off, as it inevitably does. Many couples find a warm comforting friendship as the passion wanes.
Of course, this could also be symptoms of her deliberately pulling away because she's having second thoughts about the relationship. Ultimately she's the only one who knows if this is the case.
Don't make any snap decisions. All marriages, which is what this is, have ebbs and flows. The entire relationship can't be like the honeymoon. You don't want to bail on an otherwise good relationship just because of a time of distance.
Let me refer you to a good concrete reference that can help.
Amazon.com: Feeling Good Together: The Secret to Making Troubled Relationships Work (9780767920704): David D. Burns M.D.: Books