Had A Period The Week Of Christmas. I Experienced Light

Had a period the week of Christmas. I experienced light spotting (not enough to use a tampon or pad) the 4th through the 7th of this month (January). My period was supposed to start on the 15th, I am 3 days late. Is it possible I could be pregnant? (yes I am sexually active, have sex weekly) would it be to soon to tell? Or is that possibly something else