I changed my middle name to my maiden name.
Well, this is weird, to be honest... Why did you do that?
I can't use my maiden name as my second name.
But earlier in your post you wrote that you changed your second name to your maiden name...
Sorry, but this is confusing...
Who should I reach out to sort this out?
I have no idea, I'm afraid... I've never heard of something like that... Maybe contact a Polish lawyer who's dealing with such stuff...