How can I help myself to not break down and continue being the 'rock' for my friends and family?

My friends and family consistently have problems added on to already traumatic lives and I feel incredibly selfish when I feel myself falling apart of simple things. I really want to help everyone I care about, but I'm in the midst of going through puberty, and I'm already dealing with my own problems on top of having to help everyone else I know with their problems. I don't want to complain about my life, because I know its pretty good compared to some people I know, but it hasn't been a cake-walk either. I really hate feeling like I'm not in control of my emotions. I previously was incredibly good at keeping them locked up so I could be the 'rock' for everyone who needed my help. I built up a reputation for being a very stable and calm individual who could handle anything that was thrown at me. I was known for helping people out and knowing just the right thing to say, but after a chain of events that I don't wish to discuss[Synopsis: One of my friends died because of this chain of events and everyone has been very depressed], I've been left completely drained. I no longer have any idea what to say to any of my friends when they come to me for advice and I feel like I'm letting them down. Since I've been feeling hollow, everyone else's world has seemed to begin crashing down, and everyone else seems more stressed. Even under conditions like these, where a friend's death is involved, I'm known to remain calm and be the 'rock', but this time, I was just shattered. I really need advice on how to take all this stress in stride. Someone, can you please tell me how to beat back my emotions? I don't need anyone coming in here and telling me that I need to express my emotions freely. Everyone else I know is already doing that and they need someone who doesn't do that ever to be there for them. I can't let anyone know how entirely broken down I am, or they will loose faith in my bravado, and feel a constant need to look out for how I feel, which is exactly what I am trying to avoid. And please don't tell me how unhealthy it is to bottle up my emotions. I already know... That's why I sometimes feel physically ill when horrible things happen. But I have an outlet. It just really isn't enough. But again, I can't let on just how much I feel like an empty husk... Someone, please, just give me any sort of advice that you think will be able to help me not break down so I can continue to be a good support system for my friends.