Textbook vs Real
Textbook제가 미친 것 같습니다je-ga mi-chin geot gat-seum-ni-da
Real미쳤나 봐mi-chyeon-na bwa
Why Koreans say it this way
Se-ri realizing she's falling for a North Korean officer. 미쳤나 봐 is how Koreans actually say "I think I'm going crazy" — colloquial, compact, self-mocking. The textbook version sounds like a medical diagnosis.
From: 사랑의 불시착 EP10