Wi-Fi Problems on my Early 2008 MacBook runnning OS X 10.7.5

Hello. I have a Early 2008 MacBook running OS X 10.7.5. When I first got my Macbook for Christmas, it had OS X 10.5.x, and the Wi-Fi connection was running fine, even when I was two rooms away from the router. Then I bought and installed OS X 10.6.3, and then later 10.6.8, and the Wi-Fi was not as god, but it still worked (I could now only be one room away from the router). Then I bought and installed OS X 10.7.5, and the Wi-Fi got a little bit worse, but it still worked one way away from the router. Then one day, after dowloading a lot of stuff from Downloads.com, I check and find out that my Wi-Fi is not working for some reason. I have tried some tricks and tips that people have put out, and have read the major Lion Wi-Fi Issue forum post, but still nothing works. I am wondering if I should downgrade to Snow Leopard (though then I can't download a lot of apps from the App Store, and I won't be able to publish iOS games to the App Store using GameSalad). Can anyone give me advice or help me? Thanks:)