K.G.
M.,
I have the same problem. I am currently nursing my third baby who is almost 3 months old. She is starting to refuse my left side. My 1st stopped nursing on the one side completely when she was 6 mos old and my 2nd stopped when she was 9 mos old. Both of my older girls nursed until they about 18/19 mos old.
Yes my left side is considerably larger while nusing but they do even out when I am not nursing.
Have you tried nursing on the undesirable side laying down. That is one of the only ways that I can get my 3 month old to nurse on my lt side right now.
Good luck! Don't let anyone convince you that you have to stop nursing because of this! Your baby can get all the milk it needs from the one side. My children are healthy living proof of that!
K.