Me playing Hurt by Johnny Cash

http://www.youtube.com/watch?v=BzaaoPLr084

ive only been playing for a month. so what i dont understand is why does this sound so bad? im hitting the right chords, it sounds great when my instructor does it, why bnad when i do it (also i have trouble with the F if you noticed but everything else sounds bad as well) . am i playing too rough or something? Thanks for helping me out guys (dont make fun of me too much with that video lol)