Low progesterone, help.

I could not take my blood test on cycle day 21 because it was a Sunday so we did my blood work today on cycle day 22. I had my trigger shot on the 10th and I should have ovulated on Mother's Day 12th but my progesterone is so low 4.81!!! my doctor prescribed progesterone and I will be starting it today once the prescription is filled however tomorrow is 9dpo which is the most common time for implantation, I know the likelihood of having a fertilized egg is 20% or less every month so it's not likely that I would have gotten pregnant this month anyway but I'm just concerned. We've been TTC 20 months, I have Hashimoto's disease so I am on levothyroxine and I have PCOS so I'm on 2000 mg of metformin, I started ovulating on my own at 14 months TTC and was given Clomid at 17 months TTC. Then I took femara at 18 months TTC and that was a complete bust I didn't even ovulate, now I did femara and trigger shot at 20 months TTC and I found out my progesterone is low for the first time. My OBGYN never sent me for a progesterone test and last month when my RE checked my progesterone it was really low because I had not ovulated so this is the first time I've ever had a cycle day 21 progesterone test after ovulating. I know my level should be 15 or better so it's not just a little low it's very low. Now I'm wondering if this could be part of the problem as to why I am not getting pregnant. What are the chances that low progesterone will stop implantation? Every time I had an ultrasound my lining looked fine..in fact it was always on the thicker side before ovulation. My heart is shattered. I didn't expect this at all.