Help needed...Newbie tryint to get book advices?

[Ines Maria Bravo]

Im already working on my book, so far i thought of this idea but i dont know if its too soon, is it?
please tell me after you read this (P.S.-im writing this on my language, so sorry for mistakes on my spelling okay?

I was thinking that my main character, a girl, is starting school, speaking to her friends, and they thought of going on a concert the next day, blah blah, her brother (since she doesnt has her parents alive) doesnt let her go and he has something important to do at the library, so he goes with another sister of them (they are 3 brothers - a boy and 2 girls), and shes stays at home alone at night, and she thinks that shes beeing watched or beeing filmed by someone (normal things...) and this continues..
(going on) Her class decides to make her the delegate of the class ( or whatever is called) but she starts to beeing sick and she doesnt realizes that but she feels weird, and something starts to gain control on her and she starts to make strange things and the last one she did, was climbing a big tree and stay there reading a book, and of the sudden she falls down of the tree, and this boy protects her for beeing hurt, since that day he does the same everyday... (is it too much confusing? i can explain if any doubts? please help?)