Relationships of any kind are a two-way street. I don't know your full history, but from his perspective (and what you said) all you do is argue and possibly insult him. Maybe he feels attacked and doesn't feel it's worth fighting back. It is entirely possible you were pushing him away while hoping he would change entirely.
Don't shout or be angry, be constructive. If you have a fight, look at it from both sides. In the bedroom suggest he do something different, not just say he's boring in bed. Maybe you're the one boring him?
In any case, you are partners, not manager and employee. Spend a day together, do something different. I'm of the mind that nobody falls out of love, they either never had it or stopped trying.