When I went to my doc last month he did the pelvic exam and said I was around 12-13 wks then, this month I went in for a u/s and the measurement of the baby was at 13 wks 3 days.  He kept telling me I was 5 wks off (we thought I was around 18 wks @ this time).  He also measured my uterus and said 13 wks.  I was telling him there was no way possible at the latest I had to be 16 wks.  He told me that the u/s was never wrong.  Is this true? And is it possible for me to just have a small baby?  Once he looked at his notes he noticed what he wrote about my pelvic, then said we will do another u/s in 5 wks to see if the baby is growing.  This is making me nervous.  Thnx