Pregnant or imagining it?

I had unprotected sex exactly one week and two days ago. ( I am on the pill, but I take it at different times of the day instead of the same time everyday).. So I notice about 7 days before it's time to start my period & 5 days after sex (supposed to start in 4 days) that I'm lightly bleeding brown, and today is my 4th day spotting.  Could I be pregnant? Or am I just imagining it? I really hope I am!!