Hi,
His loss of libido may be attributed to the combination of medications he's taking for his medical problems. He needs to go back to his medical doctor and discuss this problem with him. He may have to be referred to a urologist to help him allay his loss of libido.
There are also many things that contribute to this lack of libido:
1. his increasing responsibilities, you have 3 children now
2. may be worried about finances, now that you have 3 chidren to support
3. stress at work
In the meantime, you can ask your husband to pleasure you in other ways aside from intercourse by the use of vibrator and oral sex.
You also need to see a marriage counselor and a sex therapist.
Take care.