I had very low progesterone, high fsh and estrogen (basically estrogen dominance which is super bad...google it!)
I'm on progesterone cream day 21/22-28, tablets aren't absorbed very well and suppositories are just messy. I have a great little compounding pharmacy in the area that does up a prescription cream and it helps with PMS symptoms too. No more cramps and the sore back is really not nearly as bad.
The problem with the pill is that much of the progesterone is lost through the liver so you're really left with no more than 10% or so of the original pill dose. So if you want to have an effective dose of 20mg per day you will have to take a dosage of around 200 to 400mg and that's a lot of progesterone to send through your liver. Your liver will eventually get overloaded trying to process that much progesterone on a day to day basis.
Read more at https://www.infobarrel.com/Progesterone_Cream_VS_Progesterone_Pills#ICZj1G5mrToRAoXb.99
You need to support your luteal phase. There are a number of ways you can naturally support progesterone in your body. Vitex helps the estrogen/progesterone balance and here's a link where they've done studies to measure which vitamins support progesterone:
https://sites.google.com/site/miscarriageresearch/hormones-and-miscarriage/progesterone-research