R u very dear to your mom,and she loved u very much, she is the center in your heart , ?
if so, this pain will stay there for a long time, cuz u lost the most important person , it is like u lost your soul, the hurting is very deep....but u hide it by playing video games and hanging out with friends,.....now the hidden hurt is coming to surface, so u get eating and sleeping trouble...
u shall find a way to let the sadness and pain to come out , dont hide it, talk to some friends who understand this or post on some forums, find some good movies, music, art to release this sadness.
only when this is healed, u can find your heart and life back in order.
if no friends can talk about this, try to find a way to give your care and love to some people, by that way brings back a lot healing too.
Sadness and dark thing in our life will make our body and brain in disorder, but same time, it will change and mold us to new .
I m also struggling my own darkness, it is so difficult, but this is why life is a lesson and school, too. a REAL big lesson and school.