My iPhone 5 charger has a shortage?

This is my second charger. They work for a couple months then start to have shortages and go dead completly. Is it the charger or my phone? I barely get it charged when I twist the cord now. Also can I exchange it at apple? Or even fix the shortage? I'm only 13 so no tools or anything.

I would take it to the apple store and see if they will give a new chord free, tell them what has happened and its the 2nd time. You can buy a new chord on amazon really cheap, I did that and have never had an issue.