Not feeling enough

I’m losing touch with my best friend (or better my brother, we consider each other like siblings) because he’s not feeling well lately and he just closed himself...I feel like I’m not enough to help him, I’m feeling so bad and selfish for thinking how much I miss him, our conversations and all.. I just wish things to come back to some months ago when everything was okay with him.. I’m so overwhelmed, and I’d need him so so much.. idk what to do...