How to switch on my iPhone 3G

my iphone3G'S battery was very low on friday night it was lower than 10% i slept without pluging it on charger. next morning i was totally powered off. i pluged it on charging continously but it does'nt get swittched on now it wednesday i kept pluged it on charging all these 6 days. it got switched on for twice but battery was 4 % i pluged it again on charging it get low to 1% then blank again.

please suggest me what should i do now?