This will be a bit of a mystery until they can see a baby in there with a beating heart, Mommy. From your last period you should be 8 weeks 1 day pregnant today, (you count back to your period, so you get two "free" weeks at the beginning of your pregnancy. With a normal period, the day your period is due you are considered 4 weeks pregnant. Confusing, I know).
So it sounds like there is a chance you miscarried in there somewhere and then got pregnant again.
Once they are able to see a heartbeat, dating the pregnancy will be easier and more reliable.