Some people are just more in tune with their bodies and are sensitive to anything happening. I for sure felt implantation happen, it was 6 days after ovulation and I was laying in bed and suddenly felt a sharp stab in my uterus which lasted a few seconds. And sure enough, my pregnancy symptoms began about 24hrs later, one being a strong aversion to coffee, which is insane because anyone that knows me knows that the only reason I bother waking up in the morning is so I can have coffee lol. And that morning, as soon as I tasted it, I got nauseous and tossed it out and at that point I knew 100% I was pregnant. I was 8 days dpo and my tests kept coming up negative till 11 dpo and dh didn't believe me but I kept saying, I know for a fact I'm pregnant, you will see in a few days when it turns positive.