ajr, I am not having any symptoms, absolutely nothing haha, which is odd for me!
So regarding pre-implantation DPO symptoms, there is a lot of debate out there, but here is my perspective: there some evidence that the body may know it's pregnant before implantation. I don't think it's a bad thing if someone has no symptoms pre-implant, and I think *most* symptoms prior to 6 DPO can be explained by the normal progesterone rise that happens every single ovulatory cycle, whether or not a person conceives, but I think there are some that could actually be due to a fertilized egg that hasn't implanted yet. For a small number of symptoms, the one that women swear are just... odd... out of the ordinary, there are two possible things: one is called EPF, and it is secreted by the fertilized egg within 24 hours of fertilization. As far as I understand it goes out into the tubes, somehow gets into the blood stream, and tells the body to suppress the immune system. It can be picked up in blood tests very soon after conception. So it is totally conceivable to me that a woman could tell that something changed in her body. It might explain extreme fatigue or a propensity to get a cold very soon after conception. Or, she may not be able to put her finger on quite what it is that has changed, but can just tell that something is different.
https://europepmc.org/abstract/med/3322417
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(77)92605-8/abstract?cc=y=
The second possible explanation is from some studies that have shown that the blasto communicates with the uterine lining before implantation. It secretes hormones into the uterine fluids that are somehow picked up by the lining itself, telling it to thicken or become receptive in some way.
https://www.jstage.jst.go.jp/article/jrd/50/2/50_2_155/_article