Scared

I’ve been on birth control since december so my body is used to it. But these past two months my period starts one/two days earlier than it was supposed to be. So I would have started while still being on active pills. If my body were to be 100% with the pack I would start on a sunday but it’s been starting on a friday/saturday. I’m supposed to get my period now. It’s sunday so my body isn’t going with starting early anymore. I’m concerned. I take my birth control at the same time everyday. I have been crazy stressed so i’m thinking that’s what’s making it late? I don’t know if I should wait longer or be scared. Yes i am sexually active and my boyfriend pulls out and has never gone in me. I know the consequences but i’m just confused why my periods are suddenly irregular. And why I haven’t started it already?