iphone 6 screen will not stay on

My phone is behaving a little weird right now. The screen is black and stays black even when pressing the home button. Funny thing is, the phone can still receive calls and text messages (it still rings and chimes), but during that time, the screen stays black. Also, I've tried resetting the phone (by pressing the home button and lock button simultaneously). The white Apple logo appears, then the screen dims after about 10 or so seconds, I type in my passcode, and I'm able to see my home screen for about a second or two, then the screen goes black again. The phone was not damaged in any way prior to this happening. No drops, water damage, etc. I'm stumped.