Low milk supply. Own when he is hungry.

My baby is 3 & half months old. Due to latching issues I was not able to breastfeed him properly in the beginning. Since he didn't gain weight his pediatrician suggested top feed. So he is in combination feeding. Since then my milk supply decreased gradually. Added to this my baby started sleeping at night continuously from 1am till 6am for past 1 month. when checked with his pediatrician he told not wake him up for feeds let him wake up on his own when he is hungry. Now my milk supply is completely very low. When I pump milk I'll get only 30 - 60 ml. I'm already taking lactate tablets twice a day and galact granules milk twice a day. By baby has started latching properly but I can't exclusively breastfeed feed him due to very low milk supply how can I improve my milk supply please help.