iPhone 5 This accessory may not be supported.

[Hello.]

I have an iPhone 5 (GSM) that I purchased about one and a half years ago. Recently I have experienced a problem where when I connect the device to a charger, it will sometimes display a message saying, "This accessory may not be supported." At first, I was not really concerned since it was displaying only about once or twice a week when I was charging, but now, It displays every time I try charging the device and sometimes does not charge it. I have surfed the web for information on this topic and found out about the cleaning the port of the device. Now I do clean the port on a regular basis but, this still didn't resolve my problem. I am using an Apple branded charger cable and an Apple branded charging block. I am very frustrated about this problem because I see that nobody else is experiencing this problem and it haven't resolved. Thank you if you have any information or instructions for my problem.