Loss of Internet speed.

On Monday (7/22), sometime in the afternoon, our 18meg Uverse internet connection dropped to unusable rates of speed of around 1-2 meg.

Since then, I have recycled the modem multiple times.  I've unplugged the modem and the data cable from the wall and let set for 20 minutes before restarting. I've restarted network switches.

So far, when I do this I can get speeds back based on online speed tests but speeds degrade back down to 1-2 meg in a matter of minutes again.

Everything in the house is impacted by the speed issues, including phones on wi-fi.

We've not experienced this issue in the years of having service.

Diagnostic tests on the router and on AT&Ts site say there are no outages in our area, so I'm at a loss as to what is happening.

Any ideas on what to check into next?  Right now, Speed test is showing Ping 194, Download 3.43, Upload .58