You have identified your attraction to children as a problem. I wholeheartedly concur. It is never appropriate to be attracted to young children. Young children are nonsexual beings. Having any sexual contact with a minor is inappropriate and illegal. Your sexual attraction to children is a problem and the sooner it can be dealt with the better.
The clinical term associated with being attracted to prepubescent children is pedophilia. In the Diagnostic and Statistical Manual (DSM) for mental health disorders it is considered a clinical disorder. Pedophilia can be diagnosed at the age of 16. Technically, an individual is only considered a pedophile if he or she has engaged in sexual activity with a prepubescent child. Based on your letter, you are attracted to prepubescent children but have not acted on your desires. Thus you would not be considered a true pedophile but without treatment you are at risk for pedophilia.
Being attracted to prepubescent children is not part of normal sexual development. What is very positive and advantageous about your situation is it that you have identified it as a problem. Once a problem has been identified it can be treated. Treatment is highly recommended in this case. Below I explain why in greater detail.
Sexual urges can be very strong. Generally, they do not simply go away. They can become stronger and more difficult to control. If your sexual urges were to become overwhelming, the risk is that you may victimize an innocent child. This would be an extremely tragic outcome. Not only would it be tragic for the victim and their family but also for the victimizer. Pedophiles are treated very harshly in our culture. If you were convicted of having sexual contact with minors, then you would most likely go to prison for many years — but it does not end there. Should you be released from prison, you would most likely have to register as a sex offender. Being a registered sex offender could significantly damage your life. Registered sex offenders are placed on lists throughout the United States. They are denied jobs and often not allowed to live in certain areas. If a sex offender moves into a neighborhood, in some states, he or she is mandated to go door-to-door announcing their sex offender status.
In addition, having inappropriate sexual desires would inhibit your ability to have normal sexual relationships. As you can see, there are potentially very serious and life-altering consequences to ignoring this problem.
It was very brave of you to write a letter but you need to take the next step and seek help. At this point nothing illegal has occurred. Everything in therapy remains confidential with very few exceptions (and this is not one of them). Going to counseling is the right way to handle this situation. Being proactive would prevent many future hardships. I wish you well. Please take care.