I lost my grandmother a year and a half ago, so I understand where you are coming from. For a long time I would just sit still and stare into space and cry or curl up into a ball.  My grandma was my everything. She was the one who would talk to me about my life since my mom didn't care and my dad was usually busy.  Her hugs were the only thing that would comfort me if I was in a bad mood. One day, I was talking to my fiance and he deals with death in the opposite way, he is so strong in those situations. My grandma met him before she passed and she loved him. He would hold me until I was done crying and then talk to me about what I was thinking about. Eventually we talked about it and I realized that she wouldn't want me to be sad, she would want me to be happy and live my life. 

I think that is what you need to do, find someone who you can talk to about it, and then try to make your life happy. If the death of your father is consuming your life, then at least try to make sure you have one 'happy moment' each day.