Internet speed now crawling at dialup speeds

Last 2 weeks my ability to go from one place to another has become ridiculously slow. I click the back button it sometimes takes 15 seconds. Same with opening email. When I open a new page (Command N) it opens instantly but once there navigation slows drastically.
Tried adding 2 OpenDNS servers. Didn't help.
Checked internet download and upload speeds twice download 20-22 upload 5
Use Airport and it's updated
Use Comcast cable modem and their fastest service
New problem as I used to be able to zip around at lightning speed. Have changed nothing.
2010 MacBook. 4Gb memory 2.4 Ghz intel core duo 250 gig HD 100Gig free
Any ideas?
thanks