Honey, you should never feel bad or guilty for wanting to help people and for feeling bad when you can't help everyone. What you are feeling is compassion and this is a great virtue to have, and sadly, one that is sorely lacking in today's world. You have no reason to feel bad or upset for the way that you feel because you want to help people like you and that you feel bad that there wasn't anything you could do for the people who lost their lives, that is not your fault. The sad truth is that like you said, you simply just cannot help everyone. You are just one person and even with that, at your age this is alot of pressure to put on yourself to expect that you could help everyone. We all wish that we could make the world a better place and take away all of the suffering in the world, but, without suffering there would be no compassion. You just have to step back and say ok I made it and now I am going to let myself be happy about that. You can still feel comapssion for the people who lost their lives, that is what makes you human, and a good one at that for the amount of compassion you obviously feel for others, but, you have a right to be happy too.
Unfortunatly, bullying has been around forever and although more and more awareness is being brought to light about this, it does still exisit. I am so happy that youu have risen above this horrible epidemic and have gotten past it, that is always a great thing to hear. I know that some people who suffer at the hands of bullies aren't as lucky as you and you feel like why you? Why did you get to live when others had to die from this? This is called survivor grief and it is perfectly normal to feel this way.
My advice to you? If you feel as strongly as your post leads me to believe that you do for anti bullying and you really want to help the people who lost their lives to bullying, then I recommend not letting them have died for nothing. Start a anti bullying campaign or club in your area. Get out there and educate people on the affects of bullying and what it does to people. Share your story and get the information out there and make sure that people know about how harmful bullying can be. This act alone will make you feel better knowing that you are actually doing something to stop this from happening to anyone else and you will also be keeping the memories of all those who died from bullying alive for their families and loved ones. And that sweetie is the best way you can help those who are gone and also to help yourself get past the grief and hurt you are feeling.