It’s really hard not to over/under exxagerate aspects of your own life, since you obviously have such a personal perspective. My only advice, and I’ll admit it’s weak, is to go at it as honestly as possible. Try and remove your emotions from about what happened to yourself, and just literally describe what happened. Then you can go into the details about how you felt.
About sharing intimate details—the best people will treat what you write as writing, as a piece of work, as opposed to a confession about the events of your life. I took a memoir class last semester and at first everyone was writing about their grandparents and whatnot, but then one girl wrote about getting raped as a little girl and the floodgates opened; suddenly everyone was writing about being anorexic and their parents dying and their first times. But the great thing about the class is that no one was ever like “Oh my god, I can’t believe this happened to you!” or “You are so weird”. Instead, they asked questions like “How does this add to the story?” or “I think it would be useful to insert how you felt at this moment in the narrative.”
And you, too, need to look at your work as just that—work. All writing is personal.