Insane battery drainage, help?

Alright so just recently, just about a week before I updated to iOS 9.3.5.. my battery is losing power SO FAST. I have done all the tricks: disabled app refresh, fetch new data, location services, keep low battery saver on.. and A LOT more. For example, from 3:30 to 6:00 my batter went from 58% to now 10%. Most of what I was doing was exploring on Safari and just checking my email but I know for sure that shouldn't have so much of an impact. I've tried to do a hard reset and let it sit for about 2 minutes but it won't work. When I charge, it'll go from like 5% and when I look 3 minutes later.. It's now at like 15%. My battery charges crazy fast and dies crazy fast. I just preordered the iPhone 7 plus but I'm scared that my carrier won't accept my phone because of my insane battery. Anyone know what I should do? My last maybe solution could be just letting the phone die on its own rather than me forcing the reset.

Help anyone??