Every boss I have ever had thinks that anyone who takes a sick day off is faking it. I would be at work and the boss and other employees would talk about the reasons why someone was away and how it was not legitimate. I used to be so scared to ring up and say I was sick, even if I was genuinely sick because I knew what the conversation would be. They just think you are making it up. I hardly ever called in sick. I would go to work sick because I was so terrified of ringing in sick.
One day at work I felt incredibly sick and told the boss that I had to go home, he didn't object. But the hilarious thing was that after I told him I felt heaps better. Maybe I was just sick of work. He he. Rofl

But basically i have never really taken sick days because I have been too afraid of what the boss would say. I have been to work many days and felt as sick as a dog and had to endure it. I do remember taking a sick day when I was really suffering with heaps of anxiety and depression. I just couldn't bear the thought of going to work. I went to the shops for something and was seen by an employee of the place I worked for. You can guess what happened. I got in trouble and was told that I had to have a medical certificate.