Whats using up my samsung?

[I hearts you]

Ok I have a samsung galaxy ace and lately ive been charging it and than it just dies quicker, heres some imformation I can give:
-i used to.charge it just before I went to bed, than during school it would last the whole day, I used instagram and messaging and a few.google searches
-i moved away and dont go to school yet so I have just been on my ipod and phone all day,
- I use viber most of the day coz I talk to my friend
- I.use instagram only rarely now coz I can use it.on my ipod
-i am now in nothern territory so I use it alot and charge.it alot coz it keeps getting low
- ive turned all my brightness down etc
- I charge it at night now and when I wake up it says charge battery 0.o
-i sometimes have to take it out its charge because we are going somewhere and I dont wanna overheat it but its does get hot while charging :/

And for the credit/data:
I.hve 500mb and I use It up really quickly lately eversince I got viber.it seems to go quick
Is viber causing it?
It says that I watch you tube which I dont
And I always close my apps


Ive had it for about half a year, ill.buy a new one when I have a job
Thanks please help x