Galaxy s4 charging problem

A

AC Question

So I recently bought an extended battery 5400ma and I'm using the stock charger. My phone will only charge around 2-3% (74%) then start going down until I unplug then replug then it starts over.

It'll charge to 100% as long as the screen is off or the phones off. I figured maybe my charger can't supply enough power to my new battery while I use it? I already did a hard reset which didn't help btw.

I downloaded a battery monitor app and it says it's charging around 400ma - 1400ma 4.0v, it'll vary. I'm hoping it's just a charger issue and if so what kind of charger should I buy? This one?