Pregnant while having sex during your period?

Hey, I had sex with my boyfriend while I was on my period. Or rather, during my pill-free week. I was supposed to start the new pack that day and I did take my pill (by the way, it was only my second pack ever). A few hours later, the bleeding changed—it was bright red at first, but now it's just pink and very light. We had unprotected sex again on the last day of my break. We did this in the weeks before too, but I got my period each time, so I (think) I wasn't pregnant. I've had various pregnancy symptoms for a few weeks now, took a test and it was negative. Could I still be pregnant..?