The first thing you need to do is talk to him. Many men are not comfortable talking about sex with their spouse. It is an area where we might find out we are not what we think we are, sexually.
Depending on how your husband is as far as communications go, you need to talk openly as you can with him about how you feel in this matter. You need to do this in a non threatening place. Talk to him while the two of you may be alone in the car, or in the living room after the children have gone to bed. The point is don't bring this up in the bedroom. You need to let him know how you feel, and what you are lacking, and at the same time find out how he feels, and what he thinks he is lacking as well.
There could be a lot of reasons for his low sex drive. There are medical reasons, such as certain medicines and health conditions (low testosterone levels and more) can lower the sex drive. Stress, such as with a job or finances can lower the sex drive. Maybe he needs to go have a physical, and check to see if any of these things are the problem.
Some men have a kind of Madonna effect, where once their wife has given birth, they have a more difficult time seeing their wife as a sexual being.
With the little information you have given, it is difficult to give any advice, but I will give this much more, in case it will be helpful.
Talk to him about your desires. Let him know explicitly, if he is one that could take it, what you are wanting. Maybe you could liven up your sex life with role playing games between the two of you. Maybe it could be improved with something as simple as just the two of you getting away, even if it is just a motel/hotel in your own town. Sometimes just a change in scenery can make a world of difference. Other things you could try would be new sexual positions than you are used to. Explore your sexuality together.
The biggest thing you can do to help your situation is to communicate. Communicate what you are missing, wanting, and looking for. For all you know, he may be hoping you would bring it up.
I hope this helps. Good luck, and great sex!