Is pain classified as medically necessary plastic surgery?

I am sorry that you are having issues about your procedure and thanks for sharing your question. I can appreciate your concern.
It is difficult to determine the source of your problems without proper examination and testing. The revision surgery would be difficult to have it covered by insurance. however, if you have an infection or bleeding, you may have coverage of the threatening condition but not the replacing implant. 
If you adquired implants extra insurance, sometimes there is coverage of surgery with implant replacement when experiencing capsular contracture.
Finally, make sure that your doctor is aware of your process. He should be able to guide you best in your care.
Wishing you the best in your journey

Thank you for your questions.
The period of time that it takes each individual to "adopt" implants and become pain free can vary from a few days to several months.
Occasionally there are individuals that never get comfortable with having implants in place.
You need to follow up with your board certified plastic surgeon who performed your surgery.
He/she can evaluate what's going on  and further recommend treatment.

Sometimes physical therapy can be helpful.
Best of luck to you.