Progesterone question

I had a previous miscarriage due to low progesterone. It was too late by the time they caught it. So I am pregnant again and requested a blood test just in case. At 5 weeks 5 days, my progesterone level was at 10. After I didn't hear from my doctor for a few days, I called him and he said it wasn't that low and that he usually only prescribes progesterone after 3 or 4 miscarriages. Is that normal? He said the studies are inconclusive that there is any correlation between miscarriage and progesterone levels.