Hello, I Had Unprotected Sex On December 15 And My

Hello, I had unprotected sex on december 15 and my nexplanon was removed on the 21st after having it in for 6 months(didnt have a period or any spotting while on it). 5 days later i had light brown spotting on the 26&27 and after that nothing but achy cramps back pain and a little nausea. Was curious on if i was pregnant so i took a test yesterday and it was negative. Kinda worried could you please help me?!