Hymen Confusion?

I always see talk about virginity and hymens. And honestly I don’t full understand where the hymen is even supposed to be? And how can you even tell if it’s not intact?

I’ve looked at diagrams online and stuff, and I’m almost worried that I don’t even have one.. I am a virgin, but I’ve had my fair share of run-ins with bicycle seats and other things that could tear it.. But there’s no scar tissue? Nothing looks torn...

(I’m almost 18 I feel so guilty for not knowing any of this but I would like to know the answer)