And when an actor cries often real tears are being produced, when an actor screams at another actor real spittle is being produced, when an actor hugs an actor they are hugging, when kissing they are kissing. Are you aware most films (porn or not) are a series of scenes that get edited together to look like a singular performance? Actors may film talking about something one day, then the next day film the scene again to get a different angle and so on. Porn films are usually made the same way.
And apparently from what info I've picked up over the years (I've only known one porn performer who was "out" about what he did and that was about 35 years ago and he didn't really talk about it much - he would go across to Amsterdam every few months for a week or two to film a video) artificial ejaculate is often used. Ejaculation shots (in both meanings) may all be done on the first day of filming when the male performers ...er... are at their peak production. And then be edited during post production to appear towards the end of the movie. And like in other non-porn movies many scenes in in which actors are apparently engaging in "real" sex acts may not in fact be "real".
That 30 minute porn movie may have been made over several days, stopping and starting the actors repeatedly to get a better camera angle, to change the lighting, to retake a scene because someone got cramp in their leg, for them to grab a break and have a nice cup of tea, and so on. That is not what I would call real sex. (Albeit stopping to have a break and a nice cup of tea does sound rather appealing these days.)