I am so sorry to hear that your son is having such a hard time. I know what you mean when you say the look in his face makes you sad! When my son was dx with this *******Disease, I use to look in his eyes and see the worries. As a mom, you have to be strong for him, since he looks up to you and puts his total trust in you, that is the only thing that will relax him, is to know you are there for him. I also understand that you're losing it. Maybe it's time to take a little break from the hospital for you. If you have been there all along, it is starting to take the better of you. I don't know if you have a relative who could come in and spend some time with your son and you could go home and recharge your batteries. A few hours is often what you need. I hope this is a possibility for you. You will feel and think better after a little break and then your son will feel your energy level being up and his will go up also and it will give him courage.
Please know that I am sending you positive energy and I really hope your son gets better very soon. I just wish I could give you a big hug and a shoulder to cry on, as I know that as a mom, we take it at heart. But please remember if you're better your son will be better too.
Keep faith and take care of yourself. We are all with you and sending healing vibes your way!!!