While I don't have any advice, I do know how you feel. I lost a beloved dog, and my heart was broken. I cried my eyes out daily for weeks. I can now think of her with joy, and how much she brought into my life.
If this is part of your belief system, you can connect to him on an energetic level. I did this with my dog, and she would come to me to have a visit (in a meditation or with a quiet open mind). Simply invite him in. You may be pleasantly surprised.