A lot of women bleed after their first time. 'Implantation bleeding' isn't common.

That aside, if you had unprotected sex, there is a possibility of pregnancy ~ but there is no way you could know if you are pregnant or not until your missed period.

I have PCOS and because of that my cycles are long and irregular. From the research that I've done, implantation bleeding is very common. I did bleed after my first time, I thought it was a lot at first. It has since stopped (after the 2nd day) and this seems to be fresh blood. Symptoms and an early HPT can tell me if I'm pregnant before a missed period. I just wanted other people's opinions based on their experiences. Like some people have insisted that they had implantation bleeding from day 3, while others are adamant that you wouldn't have it until at least day 6.