I used to do the same thing, but I don't think any of them were adult sites. It was all done through some kind of ads broker, and the cheques came directly from them.
Looking back, it was pretty shitty behaviour by me, but as a 14 year old boy, it just didn't even feel like a crime, even a victimsless one; it almost felt entrepreneurial.
Your 14 year old self learned the core lesson of business success.
Your parents would definitely wonder why you were receiving checks in the mail from Xpics.
Once I left the Visual Basic scripted web control running overnight by mistake...