My computer keeps switching its internet setting from Airport to Ethernet without me doing anything. How can I fix this??

My computer keeps switching its internet type from "Airport" to "Ethernet." As my computer is not connected to an Ethernet cable, the ethernet does not work, and so I lose internet connection every time it does this. And it does this two or three times a minute (no exaggeration). This means that, by the time I've changed the setting and refreshed my page, the internet type has changed again, and I'm back to square one.

So far, I've tried the following:

-Reordering the list of priorities on the "Network Preferences" page

-Going to the Ethernet "advanced" options and switching everything to either "off" or from "automatically" to "manually"

-Rendering the Ethernet inactive

-Finally, I created a new location with only airport on

Usually, doing these things makes the problem go away for a day or two, and then it just comes back again.

It's not a problem with the internet itself, as this has been an ongoing issue for the past few months, and I've switched locations three times since then.

Does anyone know how to make my computer stay on Airport, and NOT switch to the Ethernet setting all the time?