Relationship question?

What do you flutherers think about falling out of lust? My boyfriend and I have been together for almost 5 years, and while I love him very, very much, it’s much more friendly than it was before, I just don’t want to have sex with him anymore.
It’s pretty awful for both of us, and I don’t know what to do about it. I don’t want to be without him, he’s my very best friend, but I think I’ve moved on in the sex department. Has anyone else been through this?