Confused and frustrated.

I am literally so disappointed right now. Okay SOOOO, around 2 weeks ago I went to confirm my pregnancy. My primary doctor told me I was Due Oct 4th. Last week I went in for my first check up with the Ob gyn and she told me I was around 8 weeks and a few days and that I was due August 31st. NOW ,today was my first ultrasound and the ultrasound technician told me I am 6 weeks and 2 days. How is it possible that I keep getting different results? My last period was Nov. 24th. This isnt adding up.