How do I let myself grieve?

I'm not really sure of anything at all anymore. Things have flipped upside down since my father passed away. I feel numb, blank and just strange. I've cried a few times. I just don't know anymore. Nothing is normal, and yet, everything is so much the same. I can't find words to express everything I'm feeling. People have been very good and supportive. They always offer to listen if I need to talk. The problem is, I have no clue what to say or do. I can't talk about this. It's not that I don't want to. I just...can't. 

It's like there's a big empty place inside where my dad used to be. Nothing feels right anymore.