Hey dear,
Dont panic you can update to latest firmware as mentioned by alexdon
Your phone will be fine no need to worry just do 1 thing for issues (if happens only for) of battery drain/not charging/ showing error while charging, phone overheating, songs and videos stored in SD Card not showing in list.
Charge your phone just while keeping it OFF, apply it 2-3 times if problems are not solved for the first time. During OFF phone will charge fastly and completely after charging use it till 10% battery remains.
Also just update your phone to latest andriod version for new UI and better performance.
I have experienced it and now working fine on KK 4.4.2 (14.3.A.0.757