Negative pregnancy test

so I went off BC back in June but my periods were so bad I went back on july 18 which was a monday (stupid I know) I just didn't want a bad period for my vacation well I ended up getting a small period on vacation which is what I was hoping. After that I had unprotected sex on the 30th of July and started bleeding the next day for a week but it didnt seem like my period the blood was too red i assumed it was because the sex was rough and he was larger so I bleed but after that I started getting back pains and eating a lot more then by the second/third week I felt dizzy, a little sick and I had a little bit of bright red blood that would turn to brown and heavy discharge ( thought it was implantion bleeding)