How be we check out the charging port first , is there dust dirt or debris of any sort in the port itself . Often lint from your pocket will get into the port and then gt driven in further when you plug in your charger . clean it with IP alcohol and a toothpick (wood) dont root round in it with anything metal.Next is the inner part of the port loose does it move at all this isnt good . If not does the whole port move in the phone . If your comfortable opening your phone you can replace the charger port

http://www.ebay.com/itm/Samsung-Galaxy-A...

they are a plug in unit which is easily replace unlike some that need to be soldered in

heres a teardown video to help

https://www.youtube.com/watch?v=gKX3iHPK...