my laptop keeps disconnecting from the wifi?

[Wombo]

I've had my Sony laptop since September and every time I use the internet the wi-fi will disconnect or a small yellow thing will pop up and say Limited Connection. except, the wi-fi stuff (router,cables.. i dont know what its all called) is literally in my room. and on my moms Mac and other laptop the wi-fi never disconnects. please help me! do i have to change a setting on my laptop or whats up?
When I say that it keeps disconnecting, I mean like I'll be doing something on the internet for a good 10-20 minutes and then the page wont load and it'll send me to a blank page saying Network Not Available and I have to disconnect from the wi-fi and reconnect. and im tired of having to do this!