ASUS laptop battery dead in a sudden 2 weeks

May 4, 2018
My laptop's age is less than 2 years, and the battery was running fine, it would hold the power for 3 or 2 hours. Suddenly, 2 weeks ago I noticed that the battery life was very weak, it would last just 1 hour, then after a few days it was just minutes, and now, I can't use the laptop without plugging it. Worse than that, when plugged, after a few minutes playing something or just using it normally, the system shuts down, as if battery was dried. My point is, the progression was just too fast for the battery to die like that, and the last issue I described suggests there is something else wrong, not just the battery. Already tried to remove the battery, reinstall the drivers, assemble again. Nothing works (battery still at 0% charge). Plus, there's something else, whenever the laptop is off, I plug it and the system boots without pressing the power button. It just boots itself when charger is plugged. Help pls!
Running ASUS model X540LJ-XX060T, purchased on August 2016. Battery icon message says "plugged in, charging".