5 Weeks pregnant, is my boss being unfair?? Do I have a right to be so upset???

I'm really having a hard time with my boss. To give you a little background, he's very egotistical (he thinks he's a God), self-centered & very unstable (he's on several anti-depressants, sleeping pills etc). I have just as much experience in the insurance industry as he does....if not more. He treats everyone like sh*t in the office and talks to us like we're all children.....very demanding and half the time, he doesn't even know what he's talking about! Last Friday, he was in one of his tirades and flipped out on me because he said I looked at him like he was stupid....WTF??? He screamed at me and then threatened my job. I was sooo upset all weekend! I'm leaving tonight for a work related convention and have a two hr drive. I normally work 9-5 so, I told him I wanted to leave at three so that I could pack, eat and take a nap. I'm 5 weeks pregnant (he knows it) and morning sickness kicked in last night. I'm so tired I can't keep my head up and HE WON'T LET ME LEAVE EARLY!! He