I think my boss is thinking of firing me? What do I do? How can I be sure?

I think you are being paranoid. All of these things are perfectly normal incidents that we must all endure throughout a regular day. Sometimes our imaginations take over and they seem bigger than they usually are. It can makes us feel people are picking on us. Oh yeah, dogs die. It happens and is usually the last thing they do. Chill out. Do a good job at work. Don't let the knives worry you. I live in Detroit where everyone carries a gun. If I worried about it, I would never get any sleep. Do not struggle. Go with the natural flow of the universe and you will be much happier