Spotting?

Hello

So I’ve only been sexually active for about six weeks (we’re both adults) and we’ve been using spermicide and also condoms. Last Sunday we had sex and then the following Tuesday night I had some light bleeding. This was about a week before my period. So I thought maybe it was implantation bleeding but since then I have taken a pregnancy test that was negative and also gotten my period. Just wondering what could have caused the spotting? Is it because my body is new to the penetration?