had withdrawal bleeding and still pregnant?

I took my first pack of pills on the first day of my period (Oct.3)...after the 14th pill (Oct.16), we decided we wanted to have a baby. The next two days (Oct.17&18), we had unprotected sex before I left for my parents. On Oct.22-25, I had what I believe was 'withdrawal bleeding' and felt very nauseous. Could I still be pregnant even if I had withdrawal bleeding? I heard some people say it does not necessarily mean you're not pregnant, simply the effect of stopping the pills abruptly. But I need to know if this is indeed the case. And if there's a possibility of me getting pregnant, how soon can I use a pregnancy kit? Thank you!