Stomach growth measuring behind..

I am 35w2d and my baby is 2.5 kg and last week also he was measuring the same infact 100gm more but today I went to see the doc as my baby was not moving less than usual and Doc told me that ya of tummy is 33w1d. Till last week he was ahead in growth over all and today we got to know this now mveryworriex althoght everything else was good and fox said not to worry he might have a smaller waist line. Has anyone else has gone through this? Please reply if you have any idea