Q: iphone 5s heated and drain very fast taking lot of time to charge and heated under lockscreen.

i have iphone 5s its genrate some problems from few days firs one is its take so much time to charge and heated even under lock screen  and not using any app and batter drain now very fast no matter u use or not what u think which what happed? is this battery problem or other thing? first its drain only when used now its drain use or not heated under lockscreen.....