You do not have a right to know if you are being investigated for a crime. It is unlikely that such an investigation would go on for years without charges being brought, the police do not have the time and money for such things. Also, if you are talking about wire tapping, computers, etc., even if the police obtained a warrant for such a search, they are not unlimited. I can't imagine a warrant going on for years.
Attorney answers to questions are for general purposes only and do not establish an attorney-client relationship
No, there is no right to know if you are being investigated for a criminal offense.
If you are not a member of a criminal organization and you believe you have been under surveillance for the past several years, chances are you suffer from a mental health illness and should seek out treatment.
No, you have no right to know about open criminal investigations proceeding against you. However, you can make a public records request to find out about past cases if enough time has passed it may be disclosed. You'd have to make a request with each agency. It is unlikely that you will discover anything however.