Period before finishing BC pack??? Help!

Is it possible to start your period before even finishing your birth control pack? I went out of town this weekend and forgot my BC at home. I didn't take Saturday or Sunday's pill. Monday I took both as soon as possible then I took Monday's later that day. I did have unprotected sex that night... Ever since I've been taking my BC like normal but  I've also been feeling as if my period was approaching and today (Friday) I saw a little bit of blood when I urinated. I have 4 pills with horomones left to take... And I just don't know what to make of this situation!  Should I worry!?