Q: '13 macbook pro: selectively slow internet

Hi everyone

I'm using a 15-inch retina macbook pro from late 2013, running OS X 10.9.5

In the last few days I've noticed an increasingly debilitating problem with my internet browser.  Certain sites, such as google, youtube, facebook etc. still load instantly, but other webpages have begun to take anywhere from 30 seconds up to several minutes/never to load.  The pages that fail usually load the main text of a page but fail with peripherals like ads.  For example, attempting to load a news article on CNN.com will load the article text after a torturous delay, but will get stuck "waiting for cmg.doubleclick.net...", which I assume is referring to some advertising.  Images and video on the page will never load.   The differences between pages that work instantly and those that don't seems to have something to do with third-party ads embedded in the page. 

I am at a university with a very good internet network and I have the same problem at varying levels of severity no matter what browser I use.  I've tried switching the DNS and clearing all my browsing data to no avail, which is making me think that the problem is somewhere in my laptop.  It's starting to seriously affect my ability to get work done so any help would be appreciated.