What do I do about my xbox friend?

Recently I have been playing xbox more. I met a guy who I really click with. I don't like him like that because I don't do the internet date thing and there's a 3 year age gap. He's more like a brother to me. Anyway, he's been having some physical problems lately and he's always in a bad mood. I trust him whole heartedly and he's told me everything about him. I know that I need to be "wary" on the internet, but I care deeply about my friend and I worry. I miss the way he used to act when we first met. He's changed a lot and I know something's wrong. Is there anything I can do to help him?