If your upbringing was anything like mine, you didn't overtly learn much about sex and relationships while growing up. You probably learned how to solve algebra equations, the conflicts that led up to World War II, and maybe acquired practical skills like how to sew a button or dice an onion. While you may have gotten some biological background related to sexuality - such as an overview of reproductive anatomy and processes. Maybe, just maybe, you had some sort of formal education related to sexual health and safety.
More than likely, however, what you learned about sex and relationships came from more informal means. You probably learned how to demonstrate love and manage conflicts (in either healthy or unhealthy ways... or somewhere in between) from watching relationship dynamics around you - your parents, family members, friends, or in the media. I can almost guarantee that you received zero direct education from either school or caretakers about how to be a good lover. How to provide sexual pleasure to someone else. How to provide pleasure to yourself.
While I would describe my own upbringing as fairly liberal, the only education I remember pointedly receiving prior to adulthood was about puberty and a very (VERY) strong message about avoiding pregnancy. Coming from a single-parent household, it was instilled in me from a young age that I never needed to depend on anyone else, and that education and a career was more important than a romantic partnership. I subconsciously watched those around me navigate relationships - for better or worse. Sometimes I was able to process those things with a caretaker, sometimes I didn't.
When I became a full-fledged adult (BARF) and started studying communication in college and later sexuality and relationship dynamics, I was finally able to connect scholarship, research and theory to real-life experiences.
This may sound totally obvious, but ACTIVELY LEARNING ABOUT SEX AND RELATIONSHIPS (through reading, activities, self-reflection, practice, etc.) completely changed the way in which I engage in sex and relationships.