I have been giving this more thought. How old are the two of you? Age can bea factor here. Is he in fair condition? getting exercise can help the energy level. How many years have you been married? Yes boredom can and does creep into the bedroom. try something new. Maybe roll play or each of you write out a fantasy you could act out, or just tell each other about. Play poker for sexual favors he wins a hand you have to do what he wants , You win a hand he has to do what you want. Have you ruled out any medical conditions that maybe effecting his sex drive? Is he on any meds? Whats it been like for him at work. Stress is another thing that can really effect sexual energy. The bottom line is that the two of you have to really start communicating about this. Be direct and be loving in how you talk to him. Let him know how important this is to you. That "Brick Wall" might be his way of not facing up to what he" thinks" is his failure as a man. Yes the male ego is in play here, so be gentle in your approach. This is why I feel a councilor might be a good idea.
This might be something very simple and easy to fix.