Every X-ray or CT scan you have had, slightly increases your chance of developing cancer.
Therefore a doctor always needs to act responsibly and outweigh the benefits and the risks.
The risk increase is not big from 8 CT scans. I.e. if you are a female of 35 years your risk of getting cancer somewhere in your life increases from 37,5% to about 38%.
You can calculate for yourself on : http://www.xrayrisk.com/calculator/calculator-normal-studies.php
No, you can not reverse the eventual damage that is done from previous scans.