Slow internet connection?

My internet is somewhat slow as of lately! Not SUPER slow, i mean I can whatch videos and that kind of thing but sometimes when I click on something it will take like 10 seconds to respond! and sometimes the page wont open! Its either KIND-OF slow or very fast! I know I dont have a virus becuse this is abrand new computer and it has norton internet security 2009! Im VERY safe on the net as well! I have charter communications and when I go to speedtest.net it tells me my current download- 10m- upload 825 kb/s! I have charter communications and I am on a desktop computer thats hooked up to a wireless router, a vonage device and a modem! I only use the router for playstation 3! If im correct charter is localy shared connection wich slows you down a bit? Anyway I would be very greatful if someone could help me out here!