When sex lives dwindle and conversation ebbs, we must assume that anger is smoldering beneath the surface of the relationship. And, when anger is not properly addressed and resolved, the result is a relationship that cools-off. What you both are trying to cool is your anger, but, the problem with putting your anger to sleep is this: the relationship goes to sleep as well.
To get past this arctic freeze, I suggest that you read through my Ten Tips. Once you are clear on how to discuss anger constructively, then start talking with each other. Say to your partner: How do you think our relationship is going? Ask him what he thinks is missing? Ask him to tell you how you could be a better partner to him? Ask him what resentments he is harboring against you. And, make room for yourself to share. Be honest with each other. The more you both openly discuss your thoughts and feelings, the less cut-off from each other you will feel. After you have a few talks, please e-mail me again and let me know how you are doing.