Your father wants normalcy in his life and you being bisexual doesn't do that for him. He probably is an old school guy that swaps stories with his mates whenever he has time and you best believe you come up for discussion. He will deflect and not talk about your secret because it will embarrass him in the process. A man who is so caught up in the thoughts of others judging him, that he can't live his own life.
Forget the fool and live your life for yourself. When he is on death's door and remembering his life, he will cry like a little bytch for not accepting his son.