"spent the whole week with his face in a toilet."
 From what we learn from chapter one, I suspect that this isn't much different from his life in school.
 "He put on his coat and got into his piece of shit car."
 He has a car? He's a senior? With all this hard luck I'd thought him a freshman. Just so you know, even having a crummy car makes a high school boy appear fortunate.
 The sister wheeled the car into a barrow?
 There ought to be a new paragraph whenever there's a new speaker.
 Derek telling off Stacy makes him seem far from pathetic. Is that what you're going for?
Author's response
Man I wish all my stories got this much attention!
I see what you mean about his life always in the toilet but time Derek spent the time puking instead of getting swirlies.  And at my school every senior had a car so I didn’t view it as much of a blessing especially for Derek; to him it was just one more thing for his classmates to vandalize and being a freshmen and getting teased would be normal, being a senior that gets treated like a freshmen, now that demeaning.  And Derek told off the girl because he wasn’t planning on living much longer anyway so he didn’t really care, think of it as a last laugh.  Thanks for the pointing out the errors I have corrected them