I'm on birthcontrol, I was suppose to start my period yesterday which was a Sunday and I didn't also today it hasn't came on. I haven't had sex either

Yes, it can sometimes happen, especially if you recently started with birth control. It may also be that your period is just off a couple of days, which can also be normal even without birth control.

That can happen yes. Did you take your pills late last time you started them?

Yes it can happen-believe it or not it happens to me eevrytime if the 7 day break happens while I'm traveling! 2 days late... and on birth control.