Why is it not charging

Hi! i have been using iphone 4 till now because it's durable than other new ios devices and i was wondering if anyone could help me with my problem.

My problem is that my iphone 4 won't charge and sometime it will charge and overheat. i already change my battery so i think that the battery is not the problem here also i notice that when i hold the power button there is no indicator showing that it's low on battery. i assume that it has something to do about the battery but then again i charge it overnight and it still has no power. anyone got a solution? help is very much appreciated thank you.