Right boob bigger than the left

Petite
I breastfeed my son. My right boob is bigger than the left. I've tried to feed him on the left one the majority of the day so that one will fill up like the one on the right but it's still uneven. I've been pumping my right one as well. It's not a huge difference but I notice it when I take a shower. Any advice on how to make my breasts the same size?