Jerky internet on MacBook Pro
Here's a few things you can try...

Firstly, (as a test) try moving closer to your wireless router until you are along side it. If the dropouts reduce, there may be something interfering with the wifi signal (especially if it is on the 2.4Ghz band - which it probably is). Have a think about what you might have transmitting on this frequency... Cordless phone, baby monitor etc. If you have either, try switching them off.

Load safari and visit www.speedtest.net
As you run the speed test, watch the graph.
This will at least give you a visual interpretation of the problem - but not actually fix it. You should be able to 'see' the data transfer stopping &amp; starting - thereby verifying your problem.

Try also searching for FREE network analysis tools on the App Store. Have a look for NetSpot, Network Strength &amp; more.

The one I use is called Wifi Analyser (in the Mac App Store, and the Android Store, but by different people I believe) - The Android version displays the signal strength of your wifi (and close neighbors) as you walk around your house (or where-ever) in a graphical format. Maybe the problem is a very weak signal ?

Lastly, maybe the problem is not the wifi at all... Perhaps there is some other software running in the background chewing up all of your processing power?

Regards, Greg.