Producing less milk?

So baby is on solids 3 times a day, and nurses 2-3 times, has a pumped bottle once or twice a day (depending on how much I pump on the morning).  I've noticed that I'm pumping a lot less than I used to (usually pump 6-9oz when before it would be 16-20oz).  Baby is sleeping thru the night, and going longer sessions during the day without milk because of the food. Anyone else experiencing a drastic drop in milk supply?  I still make enough for him, but I worry because I produced so much more before!  Thank you!