You got it right in your first post. You felt pressured to do it. If it doesn't feel right for you, saying 'no' doesnt make you any less of a man, or mean there's anything wrong with you. I'm almost 21 and I haven't had sex yet (although I apparently give valuable relationship advice
,) and there's nothing wrong with not having done something just because a lot of society has done it.
If you go to a party and don't want to worry, have your designated driver keep an eye on you and make sure you don't do anything you're going to regret. Don't do anything until
you are in complete control of the situation (i.e. not drunk) and are comfortable with everything that's about to happen.