first of all I have to ask- is your husband on medication for high blood pressure? If he is, some of the medications reduce sexual interest-- so you should find out about that and see if that is interferring and if there is any other kind of medication that might not interfer with his arousal quite so much ( or a lower dosage..)
In any case, whether or not it is the medication that is dampening his sex drive, I really don't think you should take this personally. With that many children between you and intense working conditions-plus health issues- it is no wonder that either his fatigue, or stress, or distraction, or interaction with others, is undermining your sexual life together.
However you are both young and I do think some special romantic times should be reserved-- have someone come in and take care of the kids ( brothers, sisters, parents?) just a couple times a month- but have at least some time you can call your own. Have a candlelit dinner ( even at home) put on some soft music, take a bath together- get sensual and affectionate and that alone should fulfill some of your needs. Give each other a short massage and be seductive and playful-- it should generate more sexuality between you.
If nothing works, go see a couple's counselor who specializes in sexual therapy. There may be emotional or other dificulties that you , as a couple, need to deal with. Some sexuality is necessary for bonding and bliss and emotional support for the tough times. Get your husband to think about this and work with you to have more sexuality in your life together-- hard as it may be to work out-- it really is important. Don't give up!
I suppose sexual attraction could wane over time but this sounds like an unusual situation. Best of luck.
You didn't say how old your husband is. Has he had a normal sex life in the past? Just wondering. Please talk to him, have him ask questions to his doctor. Sometimes talking about a sexual problem even with a doctor can be very uncomfortable. Give him support. Hope this helps a little and best of luck.