My laptop battery keeps draining while plugged in?

I bought a new Lenovo G510 laptop two weeks ago. I've been keeping it blugged to the charger all the time. Today I noticed my batery to be stuck at 93% as time passed it dropped to 91%. When I start the laptop up it starts charging for about 10 seconds and then it stops even though it says it's charging. What can I do?

Look like is loose charging port… Unable to constant charging. Fiddle around your charging cable to verify it is charging port problem. If it is loose charging port, you need to replace the charging port.

Alternatively,
Most laptop AC adapters come in two pieces, the two pieces connect at the rectangular box piece, often called the brick. The brick connection can often be loosen, so make sure you connect it firmly.