PROBLEM SOLVED!!!!!!!!! Right now anyway. Here is what happened.
So in Apple > System Preferences > Network, the only service I had was Wi-Fi. I removed all the others as I don't use them, and figure if they are not there that's one less troubleshooting issue I need to worry about.
But... even though I had only Wi-Fi as the lone service, when I clicked the pref. cog below the services list, and chose "set service order," I saw Bluetooth DUN. I thought this was strange, as I only had Wi-Fi, and I did notice that when I turned on Bluetooth often for my mouse, my WiFi would act up. I could not remove that Bluetooth DUN listing from the order list.
So again, I was struggling to get online, and for the **** of it, I thought what if I add a Bluetooth DUN item to my service list. So I did. I got the beachball and it was very slow. However, once I added it, I pressed the '-' button to remove the service. As soon as I did that, and I mean as soon, my Wi-Fi connected and I was online again. I then went back to "set service order" and the Bluetooth DUN was gone.
Either that solved my problem since upgrading to 10.10.3, or it was a HUGE coincidence that just as I click the button I got my WiFi back.
If anyone else is in the same boat, give this a try. Before I did it, I did PRAM reset/SMC reset. I removed my WiFi service so nothing showed in the list, then added WiFi back, then Bluetooth DUN.
I'm *REALLY* hoping this did it, as it's been miserable since 10.10.3. I've never had WiFi issues and used to think people were out of their minds. I've since been bitten by the bug.
I'll post back if anything changes.
Bryan