I am so sorry for your loss, up until just a few minutes ago, I thought I would be joining you in this horrible club. I couldn't imagine trying to go back to work that soon, well i can imagine going back to work but I can't imagine actually being able to get anything done. Please be patient with yourself, your loss will affect you profoundly in many ways. For me it feels so unfair when the rest of the world is going along normally when my kid may be dying. My world stops, doesn't everyone else's? You have it even worse.
First accept that you will never get over it, but the pain will lessen over time and then you will be able remember the good times you had with him and appreciate the beautiful grandchildren that came from him.
I will pray for peace for you and the family