@Pandor Fist of all I feel soooooooooo bad for only replying now. It's super mean of me. I just wanted to only reply once I'd read your story which I hadn't done yet. School's been hectic, and I've been writing my own story, and I've been having series weekends to treat myself for the week's hard work. I think when you sent me the message I was watching House S5 - totally awesome. And yay, another House fan :)! On to business: why do you think you're doing something wrong? Your writing is excellent; I had to laser-inspect it just to find these teeny errors. As for commas (:D I do love them), a good tip is to read the sentence out loud. Wherever you feel like a pause belongs is where a comma belongs. Obviously everyone has their own opinions because people speak differently, but its a nice general rule. "I waited until his angry steps had disappeared down the stone hallway, and pulled my balcony doors open." I would suggest using 'then' instead of 'and'.
"Sure, I ran away from home and didn't listen in class, but I have principle." Use 'had' instead of 'have'.
In both: "Yes" I replied firmly. and "I'm not afraid" I said immediately. have commas before closing the quotation marks.
"I kicked off my shoes and waded in the shallow water to prove it." Use 'into' instead of 'in'.
"You must come back home immediately" -> Yvonne says this, there's a full stop/ period missing before the quotation mark.
"Heather" My mother called. The 'M' should not be capital and there should be a comma before the quotation mark.
"I swallowed up the lump in my throat..." The 'up' can be deleted. I only read the first chapter so far, but I will read the rest soon (its holiday for me now!). Keep writing! And I'd appreciate it if you would give my story a read. Thanks!