I am so very sorry for your loss. I lost my wife in a motorcycle accident in 2010, and my new wife lost her previous husband to cancer in 2011.
It's not the same as your loss, and I know that. If you're a Christian man, seek out a Christian grief counselor if you can or if you need to. I did, and she was a tremendous blessing to me.
If you are married, I will pray for you and your wife, that you will both make it through this as a team. Remain focused on your family now during this worst time of your life.
Take it from me, you can and will get through this. You will not get over it, nor will you ever want to, but you will get stronger...but it will take a long time.
For now, recognize that each minute will seem like an hour and each time you realize he's gone, you will be shocked by that feeling, especially as you wake each morning. But know this, that feeling of shock will blessedly subside over time. The horrible pain and overwhelming impact of his loss will dissipate, and time and your faith are really the only ways that will happen. Cling to your wife and trust in the Lord for all things. He has His plans and reasons, and they may never make sense to you in this life, but one day, He will explain it all as he re-introduces you to your son.