Back button not working.

Hello there. I've had the HTC 10 since release, that's around a year or two years now? And it has been a great ride.

But I'm been noticing issues coming up lately and it's really annoying. The phone shuts down ( three times so far) randomly. The battery life is really weak now, it just went down from 55% to 15% in like an hour( don't know if I didn't be playing my anime games or what)

And finally, today. My back button was not working, all of a sudden. I uninstalled some apps, ran Boost!, and restarted the phone. It now works sometimes if I keep touching it, and that's not even guaranteed.. Any suggestions? I love this phone but why are there so many problems? And they're all really recent.