Question to all you moms out there who have strictly pumped breast milk into a bottle. Since day one…

Question to all you moms out there who have strictly pumped breast milk into a bottle. Since day one my little one never latched so I have been strictly pumping so he still gets my milk. However my milk supply decreased a few days ago (by about half) and then picked back up again. And yesterday and today it happened again. Is there something I can do? I don't want to have to put him on formula. I am drinking a ton of water.