Upset with OB

I had low progesterone months ago when I was tested before getting pregnant to check for ovulation. My cycles are irregular and I don’t ovulate when I should sometimes. I’m finally pregnant after years and years of trying to conceive and I want my ob to check my progesterone level since it was low before and she won’t do it. She said they only do that after people have had miscarriages. WHY would she wait until I could possibly miscarry when she could just check to make sure NOW and try to prevent that?! I’m so confused and upset. If it was low before why wouldn’t it be low now?