Mary: In reality, what makes relationships work is compatibility. In this case, your and his needs are simply very different and incompatible. That doesn't mean that there is anything wrong with either of you.
The only answer I can give you is this: "Are you prepared to live with this the rest of your life?" If not, then it's time to recognize the incompatibility now, rather than after the two of you have three kids being torn apart in a divorce. If this is something you can't make peace with, then the kindest thing for everyone is to end it now.
A vast difference in sexual appetites is one of the leading causes of relationship problems. People with these differences can stay together, but the relationship will never be very fulfilling for either of them. I'm afraid that's the situation you're in.