That's a very interesting situation,
Inzil. Really cool.
I noticed that, although I speak English fluently - even better than my native/cradle language (Russian) - I just can't speak it when I talk to Russian-speaking people. If I know someone speaks Russian, I just cannot speak English with them. And if by some circumstance I have to speak English to my family (for example, if we have non-Russian speaking guests), I speak with a horrible Russian accent - even though I don't have one when I talk to people at school.