Why does my iphone 5 battery life die so fast?

At one point, my battery didn't die so quickly. And when it did, it would be every once in a while when I had a lot of apps running in the background / when I used up a lot of data. That's when it would get hot. But i don't know, now it's always like that. I ALWAYS kill apps in the background, lower my brightness, and it still dies quickly. For example, I could just be texting for 5 minutes and my battery will have gone down by 10%. Another weird thing is when my phone is charging, the percentage would go down.

There have been times I had zero apps running in the background, airplane mode on, brightness low, and still the battery goes down by at least 5% just from listening to music. Sometimes the percentage drops from 70% to 50% for no reason.

What's the issue? Is there an issue with the actual phone battery because I'm not the type of person to use my phone excessively for it to die so quickly. It's really annoying too, because if I text for two hours straight, then my phone is done. I know it's not supposed to be like that. And there have been times my phone died on me when I really needed it, and I didn't bring my charger because I didn't expect it to die so fast.

So please help. I know one resolution is to keep a charger on me at all times, but that still doesn't explain why my phone battery sucks

Just use it like a phone, it should last a LONG time that way.

Mine drains quick i've Tried everything and doesn't work it's just that it has small battery

It could really be the battery. For instance, a Ni-Cad battery gets a memory when you charge it. If it is at 1/2 strength and you charge it, it will NEVER take more than a 50% charge. Nature of the beast. If you use a Lithium Ion battery, they don't get a charge memory and you can charge them at 25%, 50% or whatever and they will be fully charged. Make sure you use a lithium Ion battery.