As the others here say, it's difficult to know what to say when you're not more spesific, but I would like to mention a few Things

--Child porn refers to sexual pictures/videos with people under 18 years old, not just people under the age of consent.

--Looking at child porn is not a victimless crime - children are violated because people want to watch it.

--Be aware that young girls (and adult women too, for that matter) will often feel uncomfortable and/or scared if you look at them "the wrong way", even if you don't do anything. It's a completely normal part of very many women's every day life to be concoius of their body as a sexual object and to avoid the looks of men. Even if it may seem harmless, this has a very negative impact on many young women/girls, as they're continously objectified, or feel like they are. A peace of meat walking around. I'm 34, and I still sometimes go as far away from some men as possible on the street, and avoid eye contact with men. I do have a history of sexual abuse when I was under age, but I know many women who hasn't been sexually abused who feel the same way. I don't think this is anything new, quite the contrary. But until metoo harldy anyone talked about it, cause we would just accept it as normal part of being a woman. But it shouldn't be normal for women to be afraid of men in public spaces (or anywhere else)

--Bear in mind that even if they're over the age of consent, 16-20 year old (+/-) are NOT adult emotionally, and even a 26 year old (pick a number) will seem VERY adult to them. You need to be aware of the power dynamics here. Even if you don't feel above them, they will most probably feel beneath you. I would still feel below a man 10-15 older than myself. And girls are raised to be polite, and not hurt anyone's feelings. They might smile and giggle when they really just want to scream "get away from me", but that would make them unfeminine - or so they're taught. That can make them very vulnerable, and older people need to be aware not to exploit it.

Bottom line, be aware that things you may find harmless can still harm a young girl. But I think you're very brave to open up about this, and you deserve respect for that. I can totally understand that you're afraid of talking to your therapist about it, but you need to do something about it before you risk ruining someone's life. Maybe you can find some hotline to call for information about where to get help?