My 13yo son is going through that at the moment, his mother tongue is Indonesian but after having spent about 3 years in Australia he now has to think very hard to find words in Indo.
Telugu is my mother tongue, besides Telugu, I am quite good in Tamil, Kannada, Punjabi and well versed in Hindi....English is a foreign language so I mentioned only 4 languages besides my mother tongue;))
You have no idea what a master you are. That is amazing. To me anyway. I know one language. I cannot imagine studying or working anywhere and doing as well as you do with English when you have this as a second language that is way different than any other you know.