am i pregnant?

i had unprotected sex, he pulled out (i know this is not safe and im not ever gonna do it again) and now my period was three days late (it's usually never late.) after two days of it not coming i took a pregnancy test that was negative and then the next morning i took another that was negative. i just started bleeding but it's light and sort of brownish, could this be implantation bleeding or do you think i'm not pregnant and just freaking out?