Random Bleeding and No Period?

Long story short, I was getting intimate with my boyfriend. Like we normally do, nothing different. I had an orgasm, everything was fine. Shortly after we finished I had a good amount of bleeding, like I was on my period. Then nothing, at all. I put on a pad over night and the next day and had no more blood. My period is supposed to start in a week and it never starts with a large amount of blood. Any explanations on what this could be if it’s NOT a period?

Helpppppppp