Is a relationship worth it when there is no sex?

My SO and I have been together for almost 3 years, and now we live together. But out sex life is gone, he still wants to have sex regularly but I'm almost never in the mood. Most of the time now I feel like I'm trying to do it for him and not really me. We love and adore each other very much and this sounds bad but I fantasize about other guys, strangers and none strangers but not my SO. And we have tried changing it up and stuff but still nothing yet