I think they enjoy what they do.

I almost starred in an adult film. I was really desperate for money at the time and I was going to meet this guy in a city over an hour away, I spent a while talking to him on the phone, and then I chickened out the night before. I sent him an email with a day's notice to be polite, and he replied saying he knew I was going to chicken out and started saying all these really mean things to me, and he continued to harass me for a few months. So I knew with that company they did not treat their women right at all.

But if you know what you're doing you could find a reputable agency, and I think girls really do enjoy what they do.

And what about the guys? Are they not exploited as well? I mean, all they show is their penis, they rarely show their face.

As far as being ashamed, don't be. Watching porn is completely normal at your age.