Period late on BC freaking out

I started birth control for the first time ever about a week and a half ago. He said it was just to help regulate my period and said I'd have some pretty heavy bleeding around my period time. Well I just realized today I'm actually 4 days late for my period and have had no bleeding or spotting. Is this normal? I've left a message at his office but in the meantime I figured I'd ask. I've never had any birth control before so I just had what he said to off of as what to expect. Freaking out a little to be honest. I haven't missed a pill either. Taken every day. He also said when I do start bleeding to just keep taking them. Someone help? Is this normal? Am I overreacting?