What Causes Light Vaginal Discharge?

I started my new pack of birth control and during the first week and a half I was on a 10 day antibiotic and during the second week I was also late taking some pills which I caused some light bleeding. I'm on the last couple days of my active pills and I had unprotected sex. Could I get pregnant/be pregnant? And even if I get my period in the next few days could I still be pregnant or would it be too late in the cycle?