I haven't had my first penis in vagina sex yet, so I don't know if butt sex counts... I'm in my mid 20s.
I definitely feel like I "haven't become an adult yet", but I'm definitely glad I waited till I had a loving and patient partner before I did anything remotely sexual.
I've known him for almost a decade, as best friends and he didn't think any less of me for (at that time of meeting him) had never held hands or kissed.
I'm glad I didn't rush things even though I was too anxious for penis in vagina sex - even his finger was too big because I was so anxious and despite lots of lube.
I'm still waiting to see why sex is so glamourised though, but then maybe I have a low sex drive.