M.C.
If baby doesn't seem to be getting enough (not putting out enough wet diapers...) you can increase your supply a few ways...
-Fenugreek is a good go-to supplement to take to increase milk supply. If you like tea, Mothers Milk tea is made with it.
-Drinking one beer each night supposedly helps. I never tried it, so I can't say for sure...
-have a nurse-in. Lay in bed with baby, and encourage as much skin-to-skin contact and have him latch on as much as possible.
-pump after each nursing session, to trick your body into thinking Baby's demand is greater than it is. Even if you aren't able to pump much out, your body will register that it needs to produce more.
Also, breast milk "evolves" with your baby, as your breasts become better at doing what they do, so you may well be producing enough, just not feeling it. It was around 7-9 months that I FINALLY stopped feeling so engorged all the time and worried I was losing my supply... but my baby was still thriving and nursed until 16 months.