I'm so sorry for your loss. Everyone grieves differently so please don't feel compelled to behave in one way or another. Sometimes the emotions are there but the tears don't come. That's okay. Don't place additional demands on yourself.
Losing one's mother is a life-changing event no matter what your age is. However, being at an age when you still depend on her makes the loss more difficult. Place your priority upon finding someone to talk to about your feelings of loss and the aftermath of her death. It would be helpful for you to see a qualified mental health counselor, if possible, because of the way your mother died, the difficulty you've been having, and your youth. Also, talk to understanding relatives about her memory. She may be gone physically but she'll always be with you.