Understanding Gestational Age Discrepancies: Ultrasound Accuracy & Conception Dates

Question
I am having a problem on determining how accurate my gestational age is my first ultra sound said i was 10w 4d then and the doctor told me i was 10w. Later i had another ultra sound that said i was 19w  and it was still dead on with what the doctor told me.. basically what i have understood is that i conceived form the first ultra sound on the 28th of may and the other on the 2 of june... is there Any way i could have connived on the 13th of june.. I am really desperate to know how accurate the dates are that i was given.

Answer
I need a little more information:  The doctor told you that you were 10 weeks at the time based on what?  Your last menstrual period?  The ultrasound dating will be compared to this date if you know it.  Were your menstrual cycles regular before getting pregnant?  Also, if you happen to remember the date of both ultrasounds that would help, especially the first one.

What is your due date?  Did your doctor change it after the first ultrasound?  (typically they will not if the ultrasound is within 5 days of your last period, but some will change it)

Thanks!