Pregnant and Quit: The CEO is the Baby’s Dad

I didn't expect to have a one-night stand with my billionaire CEO boss on the night before resigning from the company! The next morning, fearing consequences, I left anonymously. Unexpectedly, my stepsister assumed my identity, and the CEO mistook her as the one-night stand! Worse still, I'm pregnant, and the CEO rejected my resignation as the secretary! What should I do?