Site Slowdown/Hummingbird, WordPress, or Site Server?

Hey There!
Maybe this isn't a question for you guys, so I am sorry if this is off topic. Sometimes when I am working on my site and especially when I am adding media, it seems like my internet is sooooo slow. It says "waiting for [mywebsite]", but when I go to google or some other public web address it goes lightening fast! Is this problem with WordPress, my cache, or with my host server?
Thanks!
Jane