For everyone who thinks they are nuts for feeling "symptoms" 2-14 DPO, here's a little info for you to make you feel better. Bear with me, it may seem a little convoluted at first.
Before implantation, the blastocyst secretes specific substances that enhance endometrial receptivity. Successful implantation requires precise synchronization between blastocyst development and endometrial maturation. The early embryo and its surrounding cumulus cells secrete detectable estradiol and progesterone well before the time of implantation.
Conceptus-secreted progesterone may itself affect tubal motility as the conceptus is carried to the uterus. Progesterone, by action mediated through catecholamines and prostaglandins, is believed to relax utero-tubal musculature. Moreover, progesterone is thought to be important in tubal-uterine transport of the embryo to the uterine cavity, since receptors for progesterone are found in highest concentrations in the mucosa of the distal one third of the fallopian tube.
Estradiol, also secreted by these structures, may balance the progesterone effect so as to maintain the desired level of tubal motility and tone. Progesterone antagonizes estrogen-augmented uterine blood flow through depletion of estrogen receptors in the cytoplasm.
So, Estradiol and progesterone begins to elevate at conception, not implantation. On to the next point.....
Human chorionic gonadotropin (hCG) messenger ribonucleic acid (mRNA) is detectable in the blastomeres of 6- to 8-cell embryos; however, it is not detectable in blastocyst culture media until the 6th day. After implantation is initiated, hCG is detectable in maternal serum. However, due to the absence of direct vascular communication, secretion of hCG into the maternal circulation is initially limited.
Thus, during the process of implantation the embryo is actively secreting hCG, which can be detected in maternal serum as early as the 8th day after ovulation. The primary role of hCG is to prolong the biosynthetic activity of the corpus luteum, which allows continued progesterone production and maintenance of the gestational endometrium. As implantation progresses, the conceptus continues to secrete hCG and other pregnancy-related proteins, and resumes detectable steroid production.
HCG is what causes your HPT to show "positive" and will not begin to circulate in your system until implantation is initiated. Remember though, your estradiol and progesterone will begin to elevate at conception.
Okay .....onto the next point.
No one knows for certain exactly what causes nausea/vomiting "morning sickness" in pregnancy but a stong case has been made implicating progesterone, estrogen, and HCG or any combination of all three.
Progesterone and estrogen have both been listed as the cause for sore breasts and progesterone has been cited as the cause for extreme fatigue.
SO, people who say they started having sympoms a day or so after O are not crazy. Some people's bodies are more sensitive to changes than others. Remember, progesterone and estrogen start to rise at conception so some people may very well experience increased temps, nausea, vomiting, fatigue, and sore breasts.