Why do I lag in online games?

A couple months ago, I was able to play online games without any lag whatsoever. But one day, I started lagging. Now I mean the kind of lag that happens when your internet connection is slow, not graphical lag. My dad’s computer has Verizon DSL, but he has a router or whatever it’s called that lets everyone else get internet through wireless internet receivers. My computer is fine. I have Windows XP.

Before I started lagging, my ping stayed in the 65-75 range, and I could play just fine. But one day, my ping shot up to 85-95, and never went back down. Not only that, but now, for some reason, every 10 seconds or so, my ping will shoot up to 300+ for a second or two, then drop back down to 85-95 again. When this happens, my connection is lost JUST long enough for me to die somehow in the game I’m playing.

I can’t think of anything I’ve changed on my PC that would cause this. I’ve heard somewhere before that Verizon DSL gets slower over time and that you have to call Verizon to get it back up to speed, but I doubt that’s true. So if anyone could help me figure out what’s wrong, that would be great, because I might be getting Xbox live for Christmas this year and I’m afraid I’ll lag on there too :(