Lost My Best Friend

I sympathize with the last post that lost their dog Baxter. Last Thursday, I lost my best friend Billy. He was only 3 years old, like Baxter. He got his nose stuck in a small insulated lunch bag when we were out and suffocated. My heart breaks as I write this. Billy was a welsh corgi and he went everywhere with us. He followed me around the house, woke me up in the morning, and slept with me at night. I spent countless hours just lying and petting him, as did the rest of my family. He was very smart, loved to swim in our pool in the summer, and play with our two cats. I have spent most of the weekend crying and thinking of him. Everything seems to remind me of him. I can't watch any commercials with dogs in them. I've had a hard time getting to sleep at night without him. I can't believe how much this hurts and how much I miss him. I haven't felt this way since my mom died 16 years ago. I'd love to know how others have gotten thru this. And are there any books about pet loss that you can recommend? I'm back at work today, but I feel so terrible that I can't really focus on my job.
Sadly,
Billys mom, Susan