As I assume the doctor told you, 1.20 is not considered pregnant. If you are so worried, you could take a handful of home pregnancy tests starting today and do them every other day for a while. (They are really cheap at the Dollar Store, and surprisingly sensitive.) Or you could do another beta blood draw.
Women sometimes have a month where they don't ovulate, and that causes a month with no period to follow. It happens. Maybe that is what happened to you.