Don't feel bad, you sound very accepting. I think of pansexuality as being attracted to people, regardless of their gender. Men, women, transgender people, etc. I don't think a person has to have experience to know whom they're attracted to. I'm bisexual, but I've never been with a woman yet. But I know I'm attracted to women. If you want to understand more and learn how to support your son, you could ask him about it more and let him know you're there for him.