My baby is 4 months old his birthvweight was 4kg and on his 10th week vaccination his weight was checked on which they lie the baby in sleep position and got it checked ..he weighed around 7.3kg and today when he got his 14th week vaccination his weight was checked by digital scale where I'm holding the baby and stood on the machine and after I alone checked my weight so the difference was around 7.1kg why my baby hasn't gained weight he is exclusively on breast feed. and only drinking left side milk and pumping my right side milk and feeding him is there any problem please explain