Anyone elses boss undermine your pregnancy symptoms at work?

I work a laborious job in a machine shop, full time and on my feet half the day. Currently I’m 28 weeks pregnant. My boss is always giving me the biggest and harder jobs compared to my coworkers. He gets discouraged if I tell him I’ll try to get to something but can’t promise it’ll be done. He doesn’t take my words seriously it seems like he undermines what is pregnant women go through. (Mind you he has two kids) but he has compared me to his wife saying his wife never had a problem before in both her pregnancies and worked strong to the time of birth. It’s extremely discouraging to me. I am protected by the Union so I know he can’t do anything to me. But he makes me feel like shit. Like today I’m having headaches and a dizzy spell and I hurt myself pushing myself too hard and he’s constantly checking in on me I feel so pressured.