Frances,
Sometimes there is nothing we have done that can cause one side to gradually have less and less milk. This is definitely not unusual, although you may not find it comfortable.
Some babies have preference and like one breast over the other one, thus less favored one starts producing less and less. Eventually one doesn't produce at all but baby can satisfy all his nutritional needs from the other one.
Also, breasts are usually not identical and one may have slower flow of milk and naturally over a time the difference becomes more visible.
However, if it happened so suddenly, and you are sure the one is really not producing enough, could you have it checked by OB or lactation consultant (preferably)? I would want to be on safe side and get somebody see it to make sure there is nothing wrong with it.
Caffeine has an impact on our milk supply and cutting it down or eliminating should help but you may need to use some herbs to help you get back to normal. It is safe and recommended to take Fenugreek (you can find it in health food stores, in form of capsules).
Also, I wanted to tell you, if the worst happens and one breast dries up, you can still successfully nurse your lo. I have nursed my dd using my right breast practically from birth and I never needed to supplement and we are still nursing. Think also about nursing twins, one breast per baby.
You can make it. Let us know how things are going.
