Low progesterone causes miscarriage?

When I found out I was pregnant and went in for a blood test at 4 weeks, my progesterone was 2.33 and HCG was 12. I had a miscarriage at 5 weeks before I could do another blood test to confirm steadily increasing hormone levels. My OB didn’t seem bothered about the progesterone level even though she agreed it was too low for a viable pregnancy.

I am ttc currently and worried about not being on progesterone supplements.

Do doctors usually wait for multiple miscarriages to confirm hormone issue? Doesn’t seem fair.

What can I do?