going by my doctors dates my son was born 4 weeks early but going by my 1st scan 5 weeks and my period dates my son would have been 6 weeks early.

i know that doctors normaly go by 1st scans dates but my scan was a little odd they guy did my 1st scan and said yep 5 weeks but come back in 2 weeks and well listen to bubs heart beat anyway i went back 4 weeks later and bub meassured 11 weeks 1 day im not sure how that worked or works so that stuffed me up on dates coz they were so all over the place.

i guess what im asking is should i go by my dates? or the doctors? i do know my periods dates and the day i missed my peroid ect.