started On birthcontrol, 5 days late .

I typically have irregular periods but since I became sexual active I've grown concern when it doesn't come when it should . I'm 5 days late from when I should have started . I started taking birthcontrol pills March 18, I was wondering if that could be the reason I'm late . I mean a week ago I broke out and was blotted as if my period was due . Now I have really sore breast . I'm just really worried I may be pregnant . Help?