Progesterone/Miscarriage Question

So I am having my second mc (at 7 werks this time) amd just got my lab results from the last weeks. My progesterone level was at 26 at 4w2d, then dropped to 17 at 5w and finally 6 at 7w2d (but baby was already dead by then). Do you know how your progesterone levels did develop? Is this drop considered normal!? Because my doctor never mentioned anything. Or do you think this might have caused the miscarriage this time? Should I request to get progesterone next time? This topic is really on my mind right now, so I'd just love to hear about your own experiences.