Now, I have total five apps : "browser","messages","home screen","Blackberry messenger", "phone".
Good news is my phone situation did improve.It does last longer after I kill other apps.
Bad news is it still running out of battery quick. It used to last about 8 hours .Now it lasts about 10 hours or so but it does not make sense if you charge over night and it only last 10 hours
Other suggestion i need to try ?Should i turn off my wifi network ?