I really screwed up

I think youll be alright sir. I (stupidly) grew up shootng without ear plugs. Figured it would help down the road with being used to it and not flinching, go figure right? I remember two distinct times when I was in my late teens. First was when I shot my dad`s .45 ACP Glock with no earplugs. It was bad. I took about 4 or 5 shots before my hearing was nearly overwhelmed with ringing in both ears. Another time I shot one of our friend`s .300 WM w/ brake, no earplugs. And that was bad. Only took one shot that time. I could almost say it was like in the movies when a arty shell goes off next to the guy and everything is muffled with dominant ringing. Almost. That one made me a believer.

16" Colt 6920 never used to bother me. But after that .300, I dont shoot without plugs unless its a .22 LR.

You should be fine though. Both times, when I shot the Glock and the .300 without plugs, it affected me for quite a while. My hearing did come back to normal, I think. I do have a slight ringing sometimes when its real quiet out in the woods. Needless to say, I doubt I can hear like a Whitetail buck, but regular conversation dont give me any trouble. People with a New York city accent however, is another story altogether.
 
When I was a kid my family had a nice sized vineyard. My father build a carbide canon that sounded strong enough to make the neighbors drop a cup of coffee if they were not expecting it coming. It scared away the thousands of starlings that could have do extreme damage to the grapes. I never had any issue with hearing but some of my friends experienced ringing sometimes even for days. I have a good hearing and never had issues if I fire a weapon without protection. I wonder how much this vary person to person.
 
I once shot a 357 magnum out the window of a box stand while deer hunting, but apparently didn't get the muzzle or cylinder gap out the window. It was like someone in my brain just turned my ears off.

Exactly. It's like you never even heard the shot right? Just pain, ears go off for a couple seconds, then lots of ringing for a couple minutes.

Also, 5.56 is pretty loud btw. I wouldn't want to squeeze one of those off without any ear pro.