Domain working without www, then using www it fails, then back to without www now it fails

I am Hosting is on Godaddy. Not real fond of customer support these days as they no longer seem Ito offer email support - phone calls only. Which I don't usually have time for, thus why I am here.

I kept geting a 500 error. After some research was able to fix it, a typo of course. This morning got up to check the site, and it is doing something weird. if I type

mydomain.com it 

comes up as it should if I type

www.mydomain.com 

it goes to centurylink dummy site (or w/e).NOOWWW if I go back to

mydomain.com

it doesn't work either.

Checking error logs, it is clean - no errors. Now the site doesn't work. I have a twofold issue, 1. I am not versed at these name server setups as I host most my own sites on a windows rig, and it doesn't seem to have issues. 2. Past experience has shown me that a 500 error is usually my end and sometimes a typo error in my php scripts, however with no errors, it is difficult to find out what it is.

If anyone is familiar with GD backend, would you have a suggestion why this is intermittently working?

It works the first time on a "fresh" device, and then it stops. My phone it worked, but switching from www to no www will crash it. I grabbed another laptop, works, then crashes. On my tablet however, I can only view without the www. phone, pc and laptop crashes regardless.

thanks!!