Re: i bought nexus 5 on last monday my battery draining soo fast what should i do?
Welcome to AC! First of all, the Nexus 5 isn't known for good battery life, so it's not like you should expect THAT good of battery life.
Second, mobile signal isn't very good, so that will put quite some demand on battery.
And third, it's a new phone and as such, a new battery. It takes about 7 days for the battery to be able to use its full capacity, so do wait before making the final call.
Also, I'd recommend installing the apps ShutApp and Doze, which will help boost standby battery. Super useful.