[DavidPlumpton]

You are in A wondering why you are in A. You are also in B wondering why you are in B, and so on. It's all perfectly consistent.

[srtjstjsj]

I am in A, though. Maybe another me is in B, but why is this me in A?

[ulber]

'this me' in your sentence just refers to the one that is in A. Thus you seem to be asking "why is the version of me, that is in A, in A?". It just is by the definition of the object ('this me') your asking about.