Implantation bleeding myth or??

I am almost 8 days DPO & I lightly spotted a brownish color today. It didn’t even take up a whole small panty liner. I’m not cramping at all. Just developed a sinus infection over night & my boobs are super sore and feel huge (never been a period symptom). Idk if implantation bleeding is real but I’m just curious what everyone thinks. When can I test for pregnancy?. We had unprotected sex on my “highest day” of fertilization but he pulled out.