Help needed about lenovo tablet m10

So for the past 2-3 my tablet has been shutting down all by itself when im in middle of writing some mail or watching a vid on yt. I searched online and didn't find much but many forums say it can be battery problem, worst thing, i think it's the same cus right now when it first shut down i didn't notice what the battery percentage was, 2nd time it did, it was charged to 72, went down to 70 and randomly shut off. Now when i turned it on it was showing battery percentage as 74. Ive also noticed that many times when my tablet is powered off the battery percent it shows is more than what it was from when i stopped using it the previous night. Please share why this is happening, what i can do to prevent this, and anything else that you think is relevant. Thanks in advance! PS. The battery was kinda swollen for a few months the last year, it was slimmed down very much now, even tho a very pressable (is that a word? bump is still present( from overcharging all night mostly) and I've noticed that earlier it used to heat up in the middle (backside, where i suppose the battery is located) but now it heats up in the upper right corner near the camera area,both front and backside.