Definitely we are going to need more details in order to help you. What device do you have? What do you see in your battery stats? Can you easily remove the battery and replace it for a new one?
Welcome to Android Central! Charge up to 100%, then let it drain to 20-30% with normal usage, without charging in between. Then show us:
1. The main Settings>Battery screen.
2. The fullscreen battery graph screen (which shows Awake time and Cell Signal Strength).
3. The Screen category (to see total Screen On time).
4. The Cell Standby category, if present (to see Time Without Signal).