The thing is, this was a juvenile crime that you did not repeat at an adult. You would not be sent to jail, more then likely, you may have to take sexual education classes, but that would be the extent of it. And all that would do would leave you leaving empty.
You claim you knew what you were doing was wrong, but its obvious you didn't just judging by your comment. You acknowledge your actions weren't out of complete ignorance, but at the same time you were not aware of the dangers of what you were doing. You were obviously in a grey area of growing up, one that led you to doing what you did. You claimed you never made a connection. That is because you had no idea the dangers and extent of what you were doing. Even if you thought what you were doing was "bad"(and in a persons mind at your age, means nothing more just naughtiness, a 12-14 year old still has no idea on the dangers of sexual experimentation at that age, at least most don't).
You even think people should pay the price for their actions for operating on actions such as these. That shows you understand the dangers of sexual abuse, but now you realize your own juvenile mistake and it is consuming the you that desires to be "just." bottom line is mate, you were still naive and pretty much a kid at that age, just a kid with a sexual drive that you did not understand.
I know its hard to not bear the guilt, but its a bad idea to sustain it. Whats done is done, and theres no way to pay for a crime that the childish criminal did not know the extent off.
I wish you the best of luck in recovery, but you do not deserve to bear this guilt.
I would also recommend to stop using Tumblr. That site is horrible in understanding situations and tends to push a one sided agenda filled with bias and bigotry. Just my two cents on the site.