Iphone 5 charge. Connects ok but doesn't increase %

Hi,

I have a strange situation with my iPhone 5

When I plug it in it seems to be connected fine, chimes to say it's plugged in, the battery graph flashes on the screen and the lightning bolt comes on.

But the percentage doesn't increase. I just did it again and it showed 9%. Its been going for a while like this. Sometimes I can fiddle it and it will add power to the battery but mostly it doesn't. When it does start adding power I am frightened to touch it till its full again coz I'm never sure when it will allow powering up again.

Each time I plug it the chime sounds, the graph flashes and the lightning bolt shows on the home screen near the top right corner, but the actual power doesn't increase.

I read the other threads and tried cleaning the lint out, of which there was a little but as Im getting the other feedback I doubt that was the problem.

Any help would be gratefully received.

I hope I have explained myself properly..