I'm so sorry.
I expect he'll let you know when he feels more awful than good, I guess in the meantime you make the most of his life by you not letting him know when you feel that. You just love him like you are, and try to feel the joy of being with him with you're with him instead of thinking of his problem - so he can feel your love and happiness in his life and not your sadness about his trouble. And cry when he's not with you. They're so perceptive, eh?
He's a beautiful boy, he makes my arms want to hold him. I hope he lets you do that. I can just put him on my prayer list.