hwy moms I exclusively pump due to the fact my son was born with a cleft pallet the past two days my supply has decreased substantially I pump every three hours and hardly get 4 ounces all together.
when that happened to me a started pumping more frequently & drank a bunch more water. even at night if baby sleeps through it. in 2 days my supply went back up.
You can try power pumping or just adding extra sessions in to get your body to recognize it needs to make more... Also try skin to skin