Concern about period not matching with non-hormone pills

I take Sprintec 28. However, I do not get my period while I am taking the white pills (without hormones). I usually get my period five - two days before I am finished with the blue pills. So likewise, I finish my period before i am done with all the white pills and start my new pack.

My questions are:

What are my chances of getting pregant when I'm taking the white pills (no hormones) and have just finished my period and have sex?

Also, should I just take the white pills right along with my period? Meaning- when I get my period throw away the remaining blue pills and when I finish my period- start my new pack with the blue ones?