I think it is natural for physical attraction to go down or maybe disappear for a while as you grow older and have been together for so long. I woudn't worry if it's a temporary thing and it might have happened before, and you got over it.
I've been together with my DH for 15 years, married for five, and I had periods in my life when I haven't been into sex with my partner, even though on the whole I'm happy with our sex life. IMO it's natural to lose your sex drive for periods of time, especially after you have kids.
If your current state has been the case for years, then I'd be more concerned.
Can you try spending a weekend away with no children, just you and him in a foreign city, and see how you feel about sex and the physical side of your relationship? It will give you the chance to talk openly about these things in a different context, in a new place and you both might feel like you did when you first met, who knows?
I don't find domestic life and a house full of children particularly conducive to passion or physical attraction, so it could be that your environment has made you feel that way and not him as such.