How am I 6weeks pregnant and my last cycle was decmber the 8th 2012

Pregnancy calculator. You cannot be 6 weeks pregnant if your last menstrual period was dec 8th. You should be 6 weeks on january 18. This all depends on the accuracy of your last menstrual period date as well as regularity of your cycles. A sonogram may be useful in this situation to more accurately date the pregnancy.
You're not. If they are calculating from the first day of your last period you are not six weeks. More like not quite 4. If they did an ultrasound and measured 6 weeks your dates are off and i would use the ultrasound dates.