Yeah, that's a sure sign of the laptop's battery is starting to fail. Batteries usually only last about 3 - 4 years. It's time to buy a new one.
One way to prolong the life of the battery is not to charge it to 100% capacity when you are simply using it while plugged into the the A/C out (sometimes referred to as "the mains"). Some modern laptops do not allow the battery to be charged beyond 50% or 80% or something in between them (depends on the manufacturer) unless you override the laptop to do so.
Basically the theory is that when the battery is close to it's maximum capacity, the efficiency of the chemicals inside the battery to retain a charge breaks down faster than when the battery is not fully charged (or close to fully charged). In simple terms, the more you use the battery the sooner it will die.
When I use my laptop at home I just remove the battery.