Hello , exclusive breastfeeding is always advisable till 6 month of age . Breast milk is a complete food ,if you are in doubt that your baby is not getting enough milk then you can check with the baby's weight gain and urine output . Three months old baby has to pass 6-8 times urine in 24 hours and 10 g per day weight gain till 5 month .Make sure that you are breastfeeding your baby appropriately. Nurse the baby on one breast at least 30 min to 45 min with good attachment.so that baby will get foremilk as well as hindmilk and feel satisfied.even if baby cries then may be some other reason which will require your local paediatrician consultation .thank you