Iphone 5 battery charging problem?

I've had my iphone 5 for less than a year and I've been charging it to full every day so it's been less than 400 charge cycles? My iphone 5 hasn't been able to charge properly since two days ago. I would leave it there to charge and come back a few hours later to see that the battery percentage was the same. When my phone dies(1%) it will only charge until 14% and stay there. However, it could only charge until 7% today.
I doubt it has to be my battery lifespan ending as i have not even reached 300 charge cycles…
I have tried rebooting my iphone but it has no effect
it has nothing to do with my charger too
my phone shows that it is charging but the percentage never goes up
please help?!
oh and please don't tell me to call apple support or go to an apple shop…

Added (1). Awhile ago the battery shot up from 3% to 43%
sadly thatt happiness was short lived as my phone just switched off on its own and the battery went down to 29%
and it started to occasionally switch off on its own since yesterdsay

The problem is not with your charger, battery or phone software, the problem is with your phone hardware. Now how have you been handling your phone have you ever dropped it accidentally at any given time? If not then it must be a manufacturing defect and you must be refunded or have your phone replaced.