First BFP turned first chemical - Need Advice

Looking for some support today - feeling really emotional. Got my first ever BFP yesterday and was over the moon. This morning around 4am I started bleeding and it has since turned in fill blown AF now 😢 Tests are still positive but fading.

On one hand, I’m very happy that it seems that we can get pregnant but now I need to investigate why I didn’t stay pregnant. I think I have low progesterone as my luteal phase is on the short side.

For those who have had this happen, what should I ask my doctor when I go see her this week? And what are the options to treat luteal phase defect?