Progesterone and Miscarriage

I've found a few links that I've bookmarked about progesterone and I'll add to this post as I'm able to comb through more. I think that progesterone is part of my problem.

"I myself give progesterone. I'd rather take a chance on delaying a miscarriage than writing off a baby that just might make it..."

"Note: The normal level of progesterone is usually "15-20." If the progesterone level is ~13 or so, this is seen as salvageable. If the progesterone is <5, I've not really seen progesterone do any good."
From: Exercise in Early Pregnancy: Risk, Low Progesterone, and Miscarriage

Hormonal causes for recurrent pregnancy loss

Progesterone Therapy (PDF)

Luteal Phase Progesterone Level(s)

Also estrogen dominance can lead to prolactin excess and low progesterone production. Here's an article about elevated prolactin and miscarriage
High Prolactin Linked To Recurrent Miscarriage

Progesterone Therapy in Pregnancy

Possible Ways to Prevent Miscarriage

"The researchers found stress hormones such as cortisol are raised in the bloodstream, suppressing the production of progesterone - a hormone which is crucial to the maintenance of a healthy pregnancy."
From: Stress 'linked to miscarriages'

"Increased levels of cortisol are associated with pregnancy. Physical and emotional stress can also elevate cortisol levels."
from: Cortisol tests