Lauren- didn't get around to doing this earlier but hopefully this will help you understand (attached pic). during your LP there is a second surge of estrogen (the body's way of acting "pregnant until proven otherwise") in a non-preg cycle your estrogen will slump again before AF (but not as low as progesterone will since once AF starts estrogen will again be the dominant hormone). In a preg cycle it will remain elevated to help support the pregnancy. This is the "flux" I was talking about and why "fertile" CM may show up after O and why fertile CM after O doesn't necessarily mean low progesterone. Does that make sense?
Non preg cycle
Attachment 26721
LP and beyond in preg cycle
Attachment 26723