Am I pregnant or are my hormones going nuts?

Hello, my last period was on December 4/09. I was on birth control pills and my husband and I decided we wanted to get pregnant so I stopped taking the pills 4 days after I started them. (On December 10th) I had breakthrough bleeding on December 14th, that lasted 4 days. We've been having unprotected from Christmas Eve until now, but now my period was supposed to come on December 31st and it hasn't. I was just wondering what the chances are that I may be pregnant, or if my cycle is off due to stopping the pills mid cycle? I know it's not that easy to get pregnant on your first try, but the fact that my period hasn't come yet is really starting to make me wonder. I've also heard however of women who come off the pill and get their period after a few months...I really want a baby....