Did Serana and the player's character sleep together? If you ask her about the Elderscroll she says "I guess you don't learn a lot about something by sleeping with it." The Player responds "are you saying you want to know more about me?" Serana says "I guess you'll never find out" Interesting
No. It's because the Dragonborn, or the player, found an Elder Scroll. You most likely past a lot of time with it until you found that you could sell it to the Orc at the Winterhold College. You may have slept with the scroll but you still don't know a lot about it. They did not sleep together.
My guy never found a scroll. What's that have to do with Serana wanting to know more about the dragonborn
Because for most of the players, an Elder Scroll as been found. It's pre-made text. And also, Serana has an Elder Scroll.