I think what you've been experiencing is depersonalization/derealization disorder. When I was trying to understand what I was going through I learned it has something to do with certain regions of the brain not being able to efficiently commumicate with each other. It sometimes happens to 'normal' people, but it usually isn't a recurrant or persistent phenomenon for them.

I noticed the more psychological stress I was under the more intense my sense of unreality would become. There's no psychiatric treatment for it (it is another poorly researched mental health disorder, although it seems to be more a neurological dysfunction as opposed to psychiatric disorder). Ironically, it is also a side effect one can have in response to treatment with and withdrawal from psychotropics often prescribed in the practice of psychiatry.

It could be due to medication, extreme stress, trauma (neurological or psychological), or...sigh. My pdoc didn't recognize it, multiple therapists didn't recognize it, but people on the internet did. They also had advise in ways to cope with it, which is more than I can say for the trained professionals I've encountered. It's still a good idea to talk it over with them, even ask them to investigate it so they can provide some input (give them honework for a change!).

The best advice I found was to do my best to ignore it, which is basically trying to avoid the psychological stress it can provide. I have found that, in general, mitigating stress is the most helpful thing I can do at this point. I can deal with sorting through what it is to feel or not feel when I'm less destabilized by stressors.