On December 23 I Had Sex, It Was My Second

On december 23 i had sex, it was my second time. I bled right after and it hurt so not sure if it was my period . on january 22 i got stained i got scared since ive heard of implantation bleeding i took a pregnacy test and it came out negative that night i had back pain and heavy bleeding since i woke up and my pad was fully stained and so was my bed . i also woke up a little emotional on sunday it went back to just a little stain red blood and on monday also stain but this time darker blood today i knoticed light brown discharge on my pad , is this implabtation bleeding or my period ? Although im scared about thr brown discharg i dont usually get that.