I testes with frer 5 days before my period and i got this result its bfp

Tmrw is my af due date and today i am having brown discharge when i wipe and little on my panty with back pain but i had all other preg symptoms i ran to urgent care they did a urine test with regular pregnancs test it came back negative i am so down

I trusted frer and i know its a good brand

What is happening?

Note: i did not have implantation discharge yet when i tested five days ago