My heart goes out to you in this sudden loss. Having experienced this I know that this is a pain like no other.

Time will heal this hurt and it can be replaced with all of the wonderful memories you have of your time together.

He isn't gone - he is just waiting for the time when you can be reunited again.
But for now try to console yourself with the fact that you did the very best thing for him - he is not in any pain and he continues to love you more than anything.