No delay to 1-3 sec delay!

Hi there, so this all started a couple of months ago well into the height of the coronavirus. I use to have near-perfect ping (78-80 ms) when playing any games, there was no delay with the controller movement and my input to move was basically flawless.  Also, I have the 1 gig download speed with Xfinity so I have the best of the best. Then one day my internet went out for a couple of hours, no worry, we just called a tech to come over to fix our outside box or whatever and got our internet back up and that is when I started to notice my inputs are taking a little longer to respond. It wasn't those every now and then lag, it was every 3 to 5 seconds! I tried to call Xfinity to see if I can see what they did to my internet but they cant look up there own employee and see what they did to fix my internet, because of that, I blame the tech for whatever he did to my internet. So I can barely play any games anymore because of how frustrating it is to try to react to something only to see my character die because it was trying to register my command.

I have tried everything from restarting the modem multiple time that I will no longer do that even if they ask me to, changed the modem 3 times now with a new one (and all 3 times were with the best upgrade you can get with Xfinity), have about 6 techs come over to my house to check the box outside (they even changed the underground wires with a bigger one to let more data come in, and it still didn't do jack), I have even bought a new router, and a new modem to see if I need more channels but none of that works. The only thing I can imagine it being and I have proof of it is that it is packet lost, I really want someone out there that actually have experiences with this to help me out and maybe even reset my internet or something because I am really tired of getting tech who doesn't have the right tools to help me fix my internet ( all 6 of the techs that helped said that everything was running fine and that there should be no problem).
If you have any question that might help you please feel free to ask, thank you.