What's wrong with my iPhone? - 1

This morning my phone was very hot it was overheating so I unplugged the charger it was at 100 and it kept shutting off so when I did a hard reset the first time the battery dropped to 95 then I did another one holding the home button and lock screen it dropped to 91 then to 88 and after that it was 88 all day until I did another reset and it dropped to 3 percent and then I came home plugged my charger in and it went up 1 percent so now I kept it in since I got home which is about 3-4 hours ago and it's still 4 percent it's not charging no battery change at all… I don't know what's going on this is the first time it's done this. It's annoying TBH, any suggestions on what I can do to fix this?

Bad battery.