Period late

I'm on the birth control pill and have been for about 3-4 months. I have an active sex life and my SO also use the pull out method. I start my pill pack on Thursday and so far I have been getting my period on Saturdays (about 3 days after I start taking the placebo pills) I just started taking my placebo pills and now it's almost Sunday and I haven't had my period. 
Am I overreacting or should I actually be worried?