my iphone 6 battery keep reducing while i pluged in and charrging!!!! what's wrong with my iphone???

My Iphone 6 is using ios 10.3.3. I've tried to restart over and over again. Tried to charge it for hours but it's still reducing battery.

When i plugged in, It was 25% and after an hour, it reduced to 1% and shut down. I really confuse and upset bout it....

Now my iphone is literally dead!!!

I plugged it into my computer and tried to use Itunes to deal with the problem. The Iphone started to charge and then the battery reduced once again. And now it shut down again. Please help!!!!!