If I understand correctly, your case and your plea and sentence were in New York, but you subsequently moved to Pennsylvania. This may be part of your problem.
Each state has different requirements for Megan's Law and each state's Megan's Law Statute is unique. As a result, the information you were given may have been correct so long as you were residing in New York, but may not have considered how the offense would be treated by another state. In other words, what you pled guilty to in New York may only be a ten year registration requirement, but that same offense (or type of offense) may be a life-time registration in Pennsylvania and Pennsylvania will treat it as such.