I’ve been with my girlfriend for a while, but what she said while discussing birth control made me think a bit. She looked at my menstrual cycles and said, “Today is a safe day, nothing will happen.” Honestly, I can’t rely on that calculation. I feel like with how advanced science is, just a calendar isn’t enough, but I’m worried that if I say this to her, it will strain our relationship. How reasonable do you think it is to believe in such calculations? Or how can I approach this conversation better?