Missed period but no early signs of pregnancy ?

I just started retaking my birth control about three weeks ago after being off of it for about two weeks . I went on vacation & ran out while I was there because my doctor was on vacation at the time & couldn't fill my prescription . I take it at the same time everyday & I'm careful . But my worry is , is that I haven't gotten my period yet . Is it the pill that is causing me to not get my period or could I be pregnant ?