Re: Less milk in 1 breast
how long has this been going on? if it's just a few days, then I wouldn't worry about it. If it's going on for a while, then you could pump that side to maintain your supply on that side.
It kind of sounds like you have an overactive letdown and probably oversupply in the left. Unfortunately, the continued nursing to relieve the ducts doesn't help with either of those, but you have to relieve the plugs. It's one of those tricky balancing acts.
Re: Less milk in 1 breast
You could pump or hand express on the side baby is not nursing from-if you don't remove the milk regularly, over time I think it could decrease the supply on that side, giving a lopsided feeling, or you could develop plugs in that breast due to not nursing. But pumping is a lot of extra work, so I think getting baby to nurse on both sides more may feel more natural and easier. Babies can nurse in thier sleep, often they can even initiate feeding-latch, in thier sleep. As long as baby is gaining appropriately there is no reason (except you wanting to get up and do something else of course) to take baby off the breast if she has fallen asleep.
If baby is getting too fast a flow on the left, she may prefer the slower flow side for hanging out and comfort nursing. Even if you have forceful letdown, there is no reason to limit feedings-in fact, limiting feeding can make forceful let down worse, and of course is the worst thing for plugs. So go ahead and offer both breasts, alternate, nurse frequently-at babies earliest cues or whenever you feel like it yourself-you don;t have to wait for a cue from baby, your breasts feeling full or mom just feeling like nursing is a 'cue' as well--you can go by how things feel at the time. This is why we say 'watch your bby, not the clock.' Once you have gotten a handle on the plugs and if you decide you have severe oversupply and want to try block nursing, that is an idea, but you would have to be careful about the plugs.
more info on plugs: http://www.llli.org/docs/00000000000...plugsblebs.pdf
and on forceful letdown: http://www.llli.org/docs/00000000000...ggrimacing.pdf
feeding cues: http://www.llli.org/docs/00000000000...eding_cues.pdf
You don't say how old baby is. There is an excellent discussion of engorgement in the new The Womanly Art of Breastfeeding, engorgement happens for many reasons & esp in the very early days it may happen not matter what mom does, but it also may be a direct result of not nursing frequently enough or baby not nursing effectively enough. If you don't have the book, you could call your local LLL Leader and have her read it to you-basically, you want to keep the milk coming out, don't try to treat engorgement by limiting feedings.