I think it's a process everyone goes through, and that happens sometimes where there is no new "excitement" in the relationship, where you feel that your love fades as everything has been at a constant.
Think about it: have you two done anything exciting or fun together over the past few weeks or months or so? Maybe a small getaway, just the two of you, would help. But if it still fades away, maybe, just maybe, you should do something about it.
Rememeber to decide wisely, good luck