Pink/Brown Discharge. Implantation bleeding?!

Ka

So my husband and I had sex on the first day of my fertile window (without realizing it was my fertile week🤦🏼‍♀️) ever since then I have felt really bad pressure almost similar to vaginal menstrual cramps, Brown/pink spotting on and off, backache, acheyness, and I’m super tired! I don’t know if I’m freaking myself out or if these are signs of pregnancy and implantation bleeding. Please help!