This thread sure has been a surprise in how it has NOT gotten nasty, or stupid.
Regarding starting late or early, myself I was a virgin to 25 and stopped being one on my wedding night. I simply was too interested in things like books, military career not to mention I wasn't all that datable. But by 20 I was no longer interested in being single.
Now I knew this girl, (hung out with her, went dancing) but I was eventually just the honorary brother type to her. Watched as she went through boyfriend after boyfriend. She's had 3 kids through 3 fathers. She married the one that gave her #3. The first 2 were utter disasters (ladies, pick a man for man for more than his meat's dimensions

). I personally think she made as many wrong decisions as it is possible to make.
My sister, I have no idea how soon she started. But she's been drop dead gorgeous all her life. She's 40+, and life has not yet decided to deliver her mr right. She's had two kids with mr absolutely f**king wrong though (she agrees about the wrong part).
So just how you end up not a virgin is largely up to you. Try and pick a fun person to find out what sex actually is. Don't kill yourself looking for a magical person, it's just sex. You put part A in part B, lots of hydraulic like activity later and you're covered in sweat and one of you has empty testicles. That's about it. It feels great. The last 15 seconds is the reason for the smile. And it's primary reason is to have children (which happens when you are stupid and don't plan in advance).
If you want a life partner, look for a life partner. If you end up having sex, fine, but keep in mind, you don't look for a life partner just for sex.
And you also don't marry a person for their appearance at age 20. Picture them old, fat, wrinkled and ask yourself, could you sleep next to that? That's how everyone generally ends up.
After childbirth, most women make great pillows