iPhone 5C battery percentage wrong

Hello my iPhone 5C has been acting really strange lately with the Battery Percentage when using apps! For example when Im using Facebook, Instagram, Vine(etc.). My battery percent would go crazy, 1 second it would be at 100% then like 5 seconds later it would be 90%. But it starts to act out more when its in the 30% range, I would lock my phone and it would be like around 32% then 5 minutes later to check the time it would be at 26% without use! And then it starts to die off after by 5 percents, It does this until it reaches 10% then it goes directly to 1 percent after that. What Ive tried to do is that I did a soft reset , when it turned back on it was like 36%. Anyone else experiencing this? Any recommendations. Need help!