https://en.wikipedia.org/wiki/Depersonalization_disorder
The Wikipedia page on depersonalization disorder contains comprehensive and well-researched information on the disorder, its development, the symptoms, the classification, as well as possible treatments. There is a separate page available on feelings of depersonalization: https://en.wikipedia.org/wiki/Depersonalization
English-language articles:
https://www.theguardian.com/commentisfree/2015/dec/29/depersonalisation-lost-my-body
https://www.bbc.co.uk/programmes/p0593jkq
https://www.psychologytoday.com/intl/conditions/depersonalizationderealization-disorder