|The problem could be the wireless itself.|
What most people don't understand is that wireless is inherently susceptible to latency and other issues that make it less reliable than a wired solution. Wireless is a convenience and you pay for that with less reliability and security than a wired solution.
The only suggestions I can make that might help to improve your wireless connection is to ensure you have the most up-to-date firmware installed on your router and the most recent drivers on the wireless interface on your computer.
Also keep in mind that those bandwidth test sites aren't really definitive. You might want to try 3 or 4 different ones and keep track of your stat's and then average them out and compare. That will give you much better idea what you're actually getting for bandwidth than running the test on one site only.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.