Why does my battery drain so fast with not much use?

[AC Question]

I charge my phone to 100% overnight and during the day im at sixth form so it doesnt get much use, normally on a morning i listen to music for about 30 mins or watch some videos on youtube for the same amount of time. this usually drains it to about 80%. During the day when the phone is in my jeans pocket I notice it gets reasonably hot (about 67C i tested it using CPU-Z). I have low battery mode on all day and run about 40% brightness

This only started happening about 2 weeks ago and at the same time i lost 4G signal and still havent been able to pick up 4G since, only 3G and H+

 

[tusk0r]

It is a saumsung s6 edge and i bought it about 2 months ago

When i click on the graph nothing happens, any ideas?

 

[hotdogchilli]

Usually, even though you don't use your phone that much, there are always background apps and the Android sistem itself, and they use the most of the battery. Try turning off all apps that are being used.