Started birth control before period

Hello I was wondering if anyone has any thoughts on starting birth control before a period starts. I'm on day 6 of my birth control back (started on the 22nd Tuesday) I was supposed to get my period yesterday the 27th. For the last 3 days all that's been showing up is brown spotting. I do have to say that I did have unprotected sex the 11th and the 20th which is before I started the birth control. So I guess that's a possible factor in what's going on. I don't know if my periods acting weird because I started birth control or if I might possibly be pregnant.