Internet is very slow at certain times?

For the past 3 days my internet has been extremely slow. All the other computers have their normal speed of internet. But mine is really slow. Like when I go on youtube and try to watch a video. I have to wait 20 minutes till it is fully buffered. I try and go on facebook. I have to wait 30 minutes to get on. and by the time that happens, it times out and I have to type my password again. But the thing I don't get is some websites load way faster than others. Like google. That loads within seconds. Yahoo, a few seconds but still faster than other websites. I looked to see if windows updated my driver because the current update for it is messed up and slows or disconnects you from the internet. It didn't so i know it wasn't the update but internet is still really slow. What happened? Is it my computer or something?