Protecting yourself with your employer?

Maybe I feel guilty because I never took time off. Last year I took maybe two sick days the whole year. This year due to being pregnant and having a lower immune system I’ve already took 4 days off.

I also had a lot issues with a bacteria infection and spotting so I took time off (made it up) for the appt.

I think my boss who is a male is getting annoyed. He told me when I told him I was pregnant that this comes first and he understand but he’s been very cold to me. I’m afraid I’m going to lose my job. I am a hard worker so if I ever get fired.or laid off it’s bc I’m pregnant and having issues. I know you can’t exactly protect yourself, but how can you protect yourself from employers?