I am not bilingual but rather can speak fluently in some foreign language. However, I constantly find myself thinking in the foreign language I know, especially

I am not bilingual but rather can speak fluently in some foreign language. However, I constantly find myself thinking in the foreign language I know, especially for topics I learned from reading in foreign books. Another simpler example is when I count I usually count in my native language, even in a specific dialect when I was taught very young!