Why have internet speeds dropped?

[Chifutbol]

So some background, I have a 2wire 3801 router. I'm with uverse, paying for 12 mb/s down. Starting about a week and a half ago, my internet speeds have dropped drastically. I'm constantly getting 1-3 mb/s down when testing at speedtest.net. Obviously frustrating. More frustrating however, is the fact that nothing has changed that should be causing this. Router has stayed exactly where it is, my computer and wireless adapter hasn't changed, there is never anything downloading. I don't even use torrents so it's not that. No one else in the house is online. It literally decided to stop working. The computer downstairs that is plugged in get 12 mb/s down. Why isn't my wireless upstairs?

 

[Chifutbol]

http://imageshack.us/photo/my-images/809/20182906.png/

Not lying by the way. That drop off where the arrow is where I started noticing lower speeds, and it hasn't gone back up since... Any ideas?

 

[Chifutbol]

Gotta get lucky to get a response here?
Can anyone tell me if they have experience with repeaters. Where I'm sitting currently, it says I have full connectivity. 5 full bars in the bottom right. And yet my internet is so bad I can't even stream Pandora. Will getting a repeater help with this? This is so frustrating, any help or ideas are greatly appreciated.