Advice HTC Sensation Battery

[razor26]

Hi, after restoring my phone to run CM12 again, I find that my battery is taking too long to charge and draining so fast. I have tried calibrating 3 times, installed greenify, cpu tuner (extreme saver) but it is still the same. In standby mode (when the screen is off and doing nothing) the battery is great and can last for many hours without losing a percent. However, when I'm using it drains so fast and the bottom part of the phone heats up (not the battery). Given this info, do you think it is best to replace the battery? Or is the problem the phone itself? Thank you.