a/s yesterday...baby measuring small

Fielding2b

The background: I was taking the 90 day cycle pills so I only had a period once every 3 months.  I went off the pill at the end of June.  1st period was in Sept. and 2nd period was 45 days later on 10/29.  Got BFP on 12/11. 

At my first appt I told the Dr. the background so she did an ultrasound to date the pregnancy.  They told me baby was measuring 4 days small but they would keep the due date from my LMP since it was not a big difference.  Due date: 8/5

At 12 week scan baby was still measuring 4 days small.  No big deal.

 At 20 week scan yesterday he is now measuring 9 days small. 

Dr. said she is not changing due date and not to worry but she does want another u/s in 4 weeks to check on baby's growth. 

 Has anyone else experienced something like this?  I know she said not to worry but I can't help it.  It's the extra 5 days that's really getting to me.  Could something be wrong and if so, what?