Hi! I am new here and looking for some help.

I went off my birth control in early January because my husband and I decided to not prevent anymore. Well recently, we decided that we wanted me to go back on it. I was due to get my period yesterday, Sunday, but it did not show up. I\'m now a day late and nothing is happening. I am due to pick up my new pack of BC this week and start them next Monday morning. So I am wondering:

-Could being off the BC cause a late/missed period this month. (Before BC I was horribly irregular)
-If I take a pregnancy test this coming Sunday and it is negative, can I restart the BC pills or should I wait just in case I might be pregnant?

Thanks!