Q: Macbook Pro 2012 Slow Internet

I bought a Macbook Pro (i7, 8 GB) about two years ago.  It seems lately the intenet on it has become very, very slow.  Often times it becomes completely unresponsive. 

It seems to go through 10-15 minute periods where

1) internet is running really slow for any page I try to go to.

2) I can search for something on Google and when I click on the link, a blank page opens up with a google address for the URL. 

3) If I can get to a web page, certain things like pictures, or sometimes banner ads will fail to load.

I mainly use Safari, but it happens with Firefox, too.   My hard drive is well under half full.  It doesn't feel like my computer is running slower overall.   

I know its not our internet.  My wife bought the same Macbook Pro with different specs (i5, 4 GB).  I run our speed tests side by side and hers finishes with 50 MB/s while mine is stil pinging to find the best server for the test.  Once completed, my test has somewhere between 5-10 MB/s.

I'm kind of at a loss for how to troubleshoot this.  I downloaded Sophos Anti-Virus to see if I have anything to worry about there.  Any other suggestions?