I have already tried more than 5 chargers but still my iPhone 5 is not getting charged. If I buy a new charger then it works fine for a week. Why is this occurring and how can I fix it?
Some iPhone 5 are eligible for a free battery replacement. Maybe that is related to your issue?
Apple has determined that a very small percentage of iPhone 5 devices may suddenly experience shorter battery life or need to be charged more frequently. The affected iPhone 5 devices were sold between September 2012 and January 2013 and fall within a limited serial number range.
You can test if your phone is eligible, on this website.