Loss of libido or loss of attraction?

SO and I have been together for over a year. The last few months sex just feels more like a chore than something fun to do. Could I have lost my libido or could I no longer be sexually attracted to him? I honestly don't know what's going on. I've never been like this before, I'm usually the initiator of sex. Any advice? I fear it might be a loss of sexual attraction, and I still want to be with him.