I am sleeping with my father

My mother died when I was just 13 years old,ever since then I took care of my father, being the only child. I became his wife and women, I sleep with him, I cook his food and I wash his clothes. I virtually did everything for him
  Now I'm 24, I met a guy some six months ago.
This guy professed his love for him,I love him too, so we started dating
This guy wants to marry me now,but my father refused. He even threatened to kill the guy.
Please what should I do,I'm confused.