Hello sravicha369,
I'm having the same issue since an Apple Premium Resseler replaced both my AirPods Pro by the end of 2020 (noise cancellation and charging problem).
I did not notice the pressure feeling in my ears when it happens, but I experience the same thing. When I'm on a call (confirmed for phone and WhatsApp, not sure for FaceTime because I don't use it often) the persons I'm talking to suddenly hear an echo of their own voice and it's really hard for them to hear me (they say I seem very far). On my side I hear them perfectly and I can't notice the problem happens until they tell me.
A quick way to solve it is to put the AirPods Pro back in the case for a few seconds and putting them back in your ears. But the problem can happen again randomly (in average between 5 minutes and 1 hour).
I also noticed that "Hey Siri" does not work when it happens. I'm still able to use Siri by activating it from the phone (However I think it does not understand me very well).
I tried all the reset methods I could find on the web but nothing worked. I went back to my Apple Premium reseller and the guy performed a complete reset of the AirPods Pro by removing it from my Apple ID and from the Bluetooth settings on my phone, holding the button on the back of the case for a long time, then coupling it to his own phone, then coupling it back to my phone. He then gave me the same advice as sterling r if it still happens ; testing it with someone else's iPhone.
It happened again.
I recently switched from an iPhone 6S to an iPhone 8 and it did not solve the issue. I'm always using the last available iOS version. That's a different phone but still with my personal settings. It's hard to test it with someone else's phone because you don't know how long it will take for the problem to appear. However the next time it happens I will try to switch to my mac without putting them back in the case and initiate a WhatsApp call from it to see what it does.
Here are some forum posts discussing about the same issue :
https://discussions.apple.com/thread/251946445
https://discussions.apple.com/thread/251528345
https://discussions.apple.com/thread/252113651
https://discussions.apple.com/thread/252540823
https://discussions.apple.com/thread/252025662
https://discussions.apple.com/thread/252313174
Now I'm not really sure what to do. Maybe calling Apple Support when it happened to show them?
I hope I helped.
Regards,
Blaise.