I have had a pretty open policy with both of my older kids from the time they were little. DS23 actually asked more questions--he always knew just how to get to the heart of the most embarrassing stuff.

But I never backed down from telling him the truth, although I do hold back on the details.
DD17 is pretty close to the vest. She doesn't share a lot, but when we get to talking she'll open up some. Sometimes I share things with her about my growing up years, old boyfriends, drugs, depression, money, college experiences, etc. She's going to be a senior so our conversations have gotten more revealing in the past year than they had been. Not long ago we had a conversation about me being a nurse and why I chose the specialty I'm in. I told her the truth--that I don't feel comfortable with men so I intentionally put myself into pediatrics and women's health. She got right to the point--"Why? Did something happen?" I had to take a deep breath--how much do I tell her? How comfortable am I with her knowing the truth? I finally decided to just say "I had a difficult childhood and some people were not very nice to me." That was all I felt I could say. The need to protect oneself is very strong. Perhaps some day we will revisit that, but for now I think I said enough.
OP, keep talking. DD and I have our best conversations in the car going out for ice cream or driving down for a pedicure. Just me and her, sitting in the dark talking. I try to let her see that I wasn't always a grey-haired, stuffy old lady and that I once faced the same teen issues that she faces now. And that some of my choices were good ones and some had consequences. She has asked me if I ever smoked marijuana. Well, that's a yes or no question. So I told her yes, I did try it in college. I didn't smoke it a lot, but on occasion I did. She ran straight into the house screaming at the top of her lungs, 'DAD!DAD! Did you know mom smoked pot in college??!!"

A-yeh, he was my rolling partner, hon.