He's beautiful. I love the photo of him sitting in the sunbeam. I am so sorry. But you gave him a gift by letting him go.
It's OK to be a wreck. As Avabear said, this IS like losing a child. And they are with us through thick and thin, unlike many "friends." I find that it comes in waves. Sometimes I'm OK, other times I'm hiding in the bathroom at work pretending to have the flu. I wake up thinking about it, which is the worst. Coming out of a dream and thinking everything is rosy, then reality hits like a ton of bricks. One of my favorite pet loss quotes is from John Galsworthy. "Not the least hard thing to bear when they go from us, these quiet friends, is that they carry away with them so many years of our own lives."
"Some of you say, "Joy is greater than sorrow" and others say, "Nay, sorrow is the greater." But I say unto you, they are inseparable. Together they come, and when one sits alone with you at your board, remember that the other is asleep upon your bed." Khalil Gibran