Am I experiencing PTSD?

My 13 year old baby boxer had been very weak and slowing down over the past week. He stopped eating and just wasn't himself.

I went out all day Sunday, but not without checking on him first. I came back Sunday night to find out that he had passed away in his cage. I started screaming and shaking him and having a breakdown. Apparently he had liver cancer and a tumor ruptured. He laid down to fall asleep and just didn't wake up.

I took him yesterday to be cremated. I have been distraught ever since I found him. My mind keeps replaying finding him and the massive amount of guilt I feel from leaving him alone is paralyzing. I can't even eat or sleep. Unless I am distracted, I keep playing that scene over and over again.

I have be diagnosed depression, anxiety and PTSD in the past (PTSD from being abused as a child).

Is it possible that I am experiencing symptoms of PTSD from finding him that way? Is it my fault that he died?