I am 13 and my 6 year old GSD has recently started growling at me. What should I do?

Hi,

I am Heather, and I have a German Shepherd. I live with my mom and 2 sisters and I am starting to see some signs of aggression. My German Shepherd is a male and is 6 years old. I e-mailed you before about him adjusting to the apartment I moved into. He had adjusted well but he has been growling at me lately and tonight he snapped at me like a bite but he did not puncture the skin. This started a few months ago when I lived in a house. He started to growl at me when I was trying to get him out of the dog house. My dad said he probably felt cornered and told the vet and he agreed. My dog has always seen my dad as the "Pack Leader." My parents are now separated and my dad lives on the other side of the world... literally in Africa so he can't really help me. Whenever my dog gets into anything like trash and I try to take it away he now growls at me. My dad has told me before that if he does this I can pop him on the mouth. I did this but it just made him more mad and growl at me more. He has always listened to my dad very well but not to me very well. He is really starting to make me nervous like when he snapped at me tonight and he is a pretty big German Shepherd and I am 13 and pretty short for my age. What can I do to stop this before it gets worse? My dog does not see me as a "pack Leader" in any way. I have tried to stand up taller make my voice stronger but it's not really working. He also playfully nips at my mom but I do not really think that is a big issue. Thank you for your time.

-Heather