Breastfeeding

 I'm a first time mom, my son is three weeks old. I exclusively breastfeed, and was curious if I'm the only one dealing with this. My son prefers to nurse from my left breast.. Do any of you moms have a baby that has a preference? He latches fine from both sides, but he is squirmy and refuses to fall asleep while nursing on the right. Also, I try to have him nurse from both sides for the same length of time, but when I pump the left side will give me 3-4oz while the right is only 1-2oz. Is there something I should be doing differently?