1. did you often drain the battery very low?
2. did you often /always have your macbook on charge,......or did you often / always BOTH have your macbook on charge AND in sleep mode?
1 or 2 are harsh on the battery chemistry and therefore its longevity
all batteries are consumables meant to replaced either in their own "due time" or early due to abuse / misuse.
The option is replacing the battery.