Ask yourself this . . . . . Is it more important to you that you have an "overwhelming desire" for sex or an "overwhelming desire" to please your husband and make him happy. You don't have to have one to have the other.
But as far as the "freezing up" part, I don't know what to tell you. Thats a part of this that I still don't understand and probably will never get. To me being in love with my wife means that I will never deny her anything that is in my power to give. Even if giving it is detrimental to my own self. So I never understood "freezing up" just becuase one spouse asks for what they truly want and need to feel good in the relationship. In my mind, that part of the equation always boils down to the self matters outweighing the relationship matters. Freezing up in this situation to me means that someone is trying to give something to the relationship with terms attached to it. And when the terms are not accepted then the contribution to the relationship is withdrawn. Loving gifts should be given freely. If it were you and you started seeing signs of hope regarding your needs wouldn't you push too? Just a little maybe?
But then again, if I had all the answers and understood everything, I sure as hell wouldn't be here on this board now would I? =)
In the end, your husband has to accept that he can't use every opportunity for intimacy to initiate sex. And you've got to figure out what it is in your psychie that is telling you to "freeze up".