My friend, losing a parent is one of the most terrible things that a child has to go through. But it is inevitable.
It is also inevitable that our grief goes through a cycle of highs and lows. Sometimes it is harder and sometimes a little better. However, as time passes, you come to terms with your loss and, as you rightly say, you become stronger. It will be up and down for about a year until you live through all the important times and days you were with him, without him. For example: You will feel especially sad on his birthday, or your birthday, during holidays, or special occasions. Once you have gone through these special days once, without him, your grief will ease a little and fonder memories of him will come to your mind. Trust me, I have lost both of my parents and I know how it goes each time.
You will never forget him, of course, but you will begin to remember him fondly, without the excruciating pain you feel now. You will miss him all the time, but it will not be as hard as it is now. And if you have a little faith, you will take courage and know that he is somewhere waiting for you and loving you all the same.
Just be patient. I know it is very hard, but it will SLOWLY pass. I PROMISS YOU. Try to not let youself stay away from people too much and do not give up your normal routine, your exercise and your work. These will help you heal quicker. Trust me.Good luck.