You poor thing - not only having a hard time in your life but off fellow ABers! It's all down to confidence honey! You gotta start believing in yourself a bit more - your opinion DOES count and by sharing your feelings on AB you've taken the first step to standing up and letting everyone know!
From what you've said, you're at school, which can be a horrible time, especially when so-called 'friends' can let you down and be mean. You've just got to remember that you're not the only one feeling this - the most confident bitchy girls at your school are probably only like that because they aren't totally self-confident. They've got to put other people down to try to make out they're more confident than they are, when really they're just following the crowd like sad little sheep - not exactly confident to do that, is it?
It can take time to find your 'voice' and be heard - but, believe me, it will happen! The more you stop saying 'yes' to everything and give your opinion, the more people will take notice. It just takes time. And perhaps it's time to start widening your circle of friends. Are there any girls at school who you think speak their minds and get respect for it? (not the gobby ones following the crowd!) Maybe befriend some of these and follow their example - or set an example and become the person that everyone wants to be like!
School is not the easiest of times - but things will get better. It just sounds like you're a bit more mature, sensitive (in a good way!) and nicer than some of the girls you hang out with.