Why is my iPhone charging acting up?

So earlier i was using my iphone 5c and it was low battery and i was dumb enough to not charge it when suddenly it died and when i was putting my usb cord to charge my phone, it said it wasnt charging even though it wasnt, so i asked a friend if my usb cord would work on his portable one, but the apple logo showed up then went away i was like what the !&&*, so i went to a deli and asked if they had a replacement usb cord but the same thing had happened, so i went outside to a charging kiosk and out of nowhere my phone was charging normally, it wasnt charging when i was using a outlet in my job but it was outside, so i went to another store and got a cord but when i came back to the store, and plugged it inside a outlet, it wasn't working but now im using a different outlet and its working there but not working anywhere else and its charging slow!

I dont know what to do please help