I'm not sure there is right thing to say, or if there is I'm pretty sure I wouldn't know what it was. What I do know is that sometimes things get to this point where intimacy goes due to a lack of communication. It is all to easy to live with someone, but get bogged down with the minutiae of life to the point where you end up living amicable but parallel lives.
You say he is your best friend. Do you tell him this? Do you do the little things we all do with a new partner - call him, text him, thank him when he does something for you, show him love and appreciation? A hundred people will jump on me and say 'ahhh well does he do that for you?'.... but sometimes it takes one to start the ball rolling.
My advice would be to hold off on the big conversations, and avoid counselling like the plague. Instead invest time and effort in your relationship again. Do things together, make each other laugh, be kind to each other, have some fun. Get a babysitter once a week and have a night out, dress up, flirt, enjoy yourself. If you can't rekindle the spark at least you can say you tried.
My DH and I didn't communicate for years, and I went off sex too. We got it back, as at the end of the day we love each other and like you guys are best friends. In my case it took the shock of his affair to start us talking. He felt rejected, unwanted, and unable to make me happy. I felt the same. Whereas I retreated into myself he went looking for 'it' elsewhere. Neither of us our proud of this period in our life, and I really recommend you don't leave things so long you risk the same.