Battle net connection laggy

This is really annoying. Ever since i got the internet from a different service provider a few months ago. I can't play online starcfraft games anymore. No one comes into a game when i host. and when i join a game it lags in the game and i immediately get disconnected.

Now I've run spybot and all the other anti malware programs, and it still does this. I'm guessing, since i Use a DSL modem hooked up to other computers, That it has something to do with my NAT settings. BUT i have no idea how i would begin to fix the NAT settings and set each household computer it's own IP adress. Maybe i should switch to cable?