My boss has no compion for other people. He threatened to fire me for being sick.?

I had the flu and was off for 3 days. There was no way I could be at work. I was vomiting, diarrhea and fever. It was bad. I had a doctors note telling me to stay home. About 4 months later, I was in the Emergency Room with pain in my side. They thought it was kidneys or appendix. After hours of testing they couldn't pin point my problem in the ER. They sent me home with Narcotic pain meds and told me to see my family doctor. When I saw my doctor the next day he said my pain is stress induced. I told him that my boss is a tyrant. He yells and screams at me. He gets in my face pointing his finger at me and swearing. It's horrible. I dread coming to work because you never know when he's going to go off. And it's not just me, he treats everyone this way. But my doctor has known me for 25 years and said this job is not worth my health. After seeing my doctor and coming back to work I was called into my bosses office. He told me my excessive absence this week is unacceptable. I told him I was in the ER and he didn't care. He said either be here or be fired. Can I sue him for verbal abuse. Can I leave this place and get unemployment. What can I do! I feel trapped.