Q: I missed the pill once - could a menstrual period mean that I am pregnant?
A: A regular menstrual period usually means that you are not pregnant.
Implantation bleeding usually happens one week after fertilization. Bleeding that happens 2 weeks afterwards is too late for implantation bleeding.
Implantation bleeding is typically just a couple of drops. If you just missed one day of birth control pills, and especially if you are bleeding now like a regular period on time, chances are that you are not pregnant, though only a negative pregnancy test will confirm this.