I think some posters would do well to remember the OP has a very sick child.
That is a polite way of telling you to shut the fuck up if you havent anything constructive to say.
OP. The chances are that you OH can look after your DS as well as you. I totally understand your feelings (and I understand shaz's as well
) but it really is better to share the care of your child.
If you dont it can lead to real difficulties. Because I tried to shelter my OH from the horrible, awful stuff that went on when my DD was ill, he never really understood what looking after her was like.
He thought I sat around reading and watching tv all day whilst he worked and look after the other DCs. So when he spent a few hours with DD he wouldnt bother clearing up after himself and I went home to a filthy house.
I thought he was a selfish twat for doing it, he thought I should be doing my 'share' whilst he had a rest at the hospital.
If I got upset and called him from the hospital he thought I was being a drama queen because as far as he knew hospital meant my DD lying in bed and having her temp taken. He just didnt see the stuff I did.
I did it to protect him. I ended up with PTSD and a DS who told me I had abandoned him 
Share the care, spend time with your other DCs.
But if you really cannot bear to be away from you DS you have every right to go to him. But not because you OH isnt capable. Because you need to be with your son and that is perfectly understandable.