Polly, your experience is very similar to mine, same age, same situation, man in his early 20s. I'm still unsure as to whether I lost my virginity that night, or was raped.
A very dear friend of mine, who I've known since my teens was raped., by a senior P.O. She'd passed her probationary/training as a PC. She went out to celebrate, got very drunk, and accepted a lift home from him, with whom she'd been flirting and chatting with most of the night. On the way home he asked would she mind if they stopped at a friend's house, that he was keeping an eye on, because friend was on holiday.
The moment they got through the front door, he locked it, did something to scare the crap out of her, (can't be more specific, too outing) and raped her. Who knows, she may have chosen to have sex with him willingly, but he took that choice away from her. Even with all her self defense knowledge and fitness levels, she froze, and he raped her. She didn't tell a soul for over 10 years.
Dfriend didn't press charges, because she'd seen all the shit that rape victims/survivors are put through during statements, then re-living the whole hideous experience in court, and having one's personal life pulled apart.
Things have moved on a bit since then (I think?) Or have they??