Sarah,

You reported that the sex frequency dropped when you moved in with him. Could it be that you are too available?

You also mentioned shift work. If he is working nights, or, if his schedule involves erratic shifts, he may develop all sorts of physiological problems - sex in part is physiological, so the drive might become compromised.

All of it is about him - his spontaneous erections, his inability to have a climax inside your vagina, your willingness to give him blow jobs without asking for a reciprocity, etc. - a whole lot about him. What about you?