Hello It's important to understand that Breast milk production in the body on supply and demand basis.The more and frequently you feed the baby the more it gets produced in the body.Please make sure that you feed the baby atleast once in the midnight so that adequate milk production happens in the morning.Also,Keep a WHO growth chart(You can download from internet) to track your baby progress.

As babies grow they mostly stop taking the night time feed . You don't have to wake him up at night to feed . The reduction of milk supply which you feel may not be actual reduction but due to the fact that as the baby grows  his requirements of milk increase.  But if your baby is able to sleep almost completely through the night while on breast feeds I feel the milk supply is adequate for the baby and you must continue to breast feed exclusively for another two months

There should be rise in weight by 300 to 600 gm in 1 month. Urine frequency 6 to 8 times in 24 hours. If both is there then need not to worry. Don't disturb the sleep pattern and allow continuous sleep of the child.