You are on birth control so what you had was not unprotected sex. Birth control prevents pregnancy. You are having your period. End of story.

Use a condom next time for double protection.

could it possibly not be a period, just implantation bleeding? like i said, i know girls who have gotten pregnant while on it. and take it regularly

If you are concerned, take a pregnancy test.

Implantation bleeding isn't common and it isn't 'like a period' at all. It is barely there.

How long have you been on birth control pills? Are you aware that your period will lessen and become lighter over time while taking birth control pills?

i have been on them for a year or so. my period has never been like this before. maybe i am just scaring myself, but it doesnt hurt to ask, yeah? thanks though.

I did get pregnant on the pill with my first child but I didn't take it per directions. I skipped one time and then took the pill at different times the same month (I think I really wanted to get pregnant at that time, so it worked out well). It is supposed to be 99% effective if you take it correctly. I did not. So, that is the next question...have you been really good at taking your pill and taking it at the same time each day? If you have, then the chances of pregnancy are quite low. I would take a test for reassurance.