Latching on demand is the best way to remove milk, regulate your milk supply, and prevent engorgement. You can try to massage your boobs and hand express some milk before latching your baby. You can google Youtube videos for more information.
A proper latch is important so that it is not painful for you. Have you tried using a nursing pillow? If not, you can try using pillows to help support your baby when he latches and ensure a deep latch. If he still cannot latch properly, you may want to consult a lactation consultant to see if he has a tongue tie.
Pumping usually will yield less as compared to latching and is not a true reflection of your milk supply. Sometimes, it could be that your pump doesn’t have enough suction to clear your boobs or the flange size could be wrong.
You can join Breastfeeding Mothers’ support group Singapore on Facebook to seek advice on breastfeeding too.