Girl trouble....heeeeeeelp me

Before i start typing the details... this is a different person (the brother of this account).
So... as i was saying... I really really REALLY like a girl. We both have some tihngs in common and we did have a share of laughs. I have a frightness of rejection.
REJECTIONOPHOBIA!
I don't know what to do, how to find out if she likes me, how to ask her out if she does, how i know if she's flirting with me, how to flirt with her without making it too obvious.
Someone please help me. I'm dying in my head. Can't stop thinking about her and i really need to let it all out. I also need to know how to get her alone with out making it too obvious to "talk".
I'm very nervous and this is the 3rd time i've ever felt like this before for a girl and i really like her. I can barely talk to her about small stuff like HOMEWORK. plz give me your honest opinion and i need to know soon before she's taken and i'll go emo for a few days (not that emos are a bad thing or i don't have anything against emos) and i just need advice what to exactly do. Thanks! OH and one more thing... my parents think i'm still too young to have a girlfriend and it might "RUIN" my future and i'll do bad in school. Also... *sigh* i'm kind of overweight... i'm 195 lbs. and she's about 90-120... don't know exactly... So plz tell me if she'll still be interested. Thanks. Give me hints andvice or any opinions.