Think of it this way: imagine it's you, and it's true.
He could have been leading a double life
I could have [could've] been leading a double life
I have been leading a double life

Conversely:
He could of been leading a double life
I could of been leading a double life
I of been leading a double life
(The Porcupine From Purgatory Ningles, mateyplops! How are the kids? *smoosh*, Mon 21 Sep 2026, 19:25, Reply)