Cân nhắc xem hai bạn hẹn hò được bao lâu. Suy nghĩ xem tại sao bạn muốn nói cho anh ấy biết. Tránh dùng cách nói gián tiếp để ám chỉ chu kỳ kinh nguyệt của bạn như "tuần dâu rụng," "ngày đèn đỏ," "tới tháng," hoặc bất kỳ cách nói tránh nào. Đừng cảm thấy bị tổn thương nếu anh ấy trốn tránh cuộc trò chuyện.

I'm interested in that, but I only have a few mins. Can you give me at most the first 500 characters of a detailed explanation in English about that?
As with most personal information, it's not always appropriate to share something intimate with a person you haven't known for very long. Boys aren't always super mature at this time in their lives, and if it makes him shy, confused, or uncomfortable he might not know how to react.  If you have been dating for a while and you feel you know him pretty well, you might want to bring it up casually. You don't need to make a big deal about it, because it really isn't a big deal! Think about how he's