EMERGENCY! Very high Ammonia levels! Please help

Hello,
I am a new betta owner. My fish is very happy and has everything he needs. He has a spacious 6 gallon tank. However I am having a lot of trouble with ammonia levels. My testing kit reads that the ammonia is at 2.0, and who knows how long it's been that high. I am very worried. My betta is behaving normally, but might be getting ammonia poisoning (black gills).
To remedy the situation, I have changed out the water and have started to filter the water during the water change. (I change the water once a week) I just bought AmmoniaSafe (Tetra) as well as SafeStart concentrated bacteria (Tetra). Will these products help? Is there anything else I can do?
Please help!
-PenelopeBetta