What you are describing is an experience sought after by those practicing "nondual" meditation. Tibetan buddhism, Advaita Vedanta, and Taoism are the major traditions in the east that practice this, though zen could also potentially be considered nondualist. I'm currently in a class taught by Michael Taft that takes a syncretic approach to teaching nondual meditation [1]. One of the best books on the subject is "Nonduality" by David Loy [2].

Michael mentioned that some people can achieve it right away with a single meditation and others take years. Sounds like you are in the former category. Unfortunately I'm in the latter.

[1] https://deconstructingyourself.com/nondual-awareness-meditat...

[2] https://www.amazon.com/Nonduality-Buddhism-David-R-Loy/dp/16...