I get derealization/depersonalization whenever I get a panic attack. Every time. And to any onlookers, it appears like there is nothing going on with me at all; other than my schizophrenia. I feel completely powerless every time.
The derealization, for me, manifests as me believing something bad is going to happen to me, like my bladder is going to explode. Or the lymph nodes in my arms are going to explode. I recently had an attack where I believed my appendix was going to explode. I am on Lexapro 30mg for it, but lately its effect seems to have diminished. And I think I am in denial of it. I know I have panic attacks, but something makes me believe that it's something worse. Like they are not really panic attacks, but something worse. But that's just my irrational nature kicking in. I just have a hard time accepting that, yes, I do indeed have panic attacks. And that they are nothing more, nothing less. They just are.
The depersonalization also happens to me during panic attacks. Like the derealization, it happens every time. I have schizophrenia, so maybe that's why I am so strongly themed to these two things; as feelings of unreality are the hallmark of psychosis. Like Rainbowstarsxoxo described, that's pretty much how I feel when I get depersonalization.