Airport Express slowing connection

[nw481]

I got a refurbished airport express around February of last year. I mainly got it for use as an access point for my ipod touch. It ran perfectly up until about 2 weeks ago, when i got a refurbished macbook (a1278). Since then my wifi has been running really slowly on the computer, but not the ipod. My wired connection has also been very slow. But if i unplug the airport the wired internet becomes at least twice as fast. Also, my macbook always has 5 bars of connection, even when it wont connect with the internet. I'm using the Comcast arris modem, which is connected to a dlink ebr-2310 router, and the airport is connected to that. I'm not sure what caused this seeing as i had used my airport express regularly for my ipod and it only started dropping and slowing connecting when i got my macbook. Any and all help will be greatly appreciated.