All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, you should endeavor to meet the requirements of sincere repentance and you should know that Allaah is Most Forgiving, Most Merciful and that He forgives all sins for those who repent from them, as Allaah says (what means): {Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allaah. Indeed, Allaah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful."} [Quran 39:53]
You do not have to inform that person about your evil thoughts; rather, you must avoid telling him or her, as this leads to great evil. Your repentance is valid even if you do not tell him or her.
You should know that a person is not sinful for having evil thoughts. In His Mercy, Allaah has forgiven our Muslim community for the evil thoughts that we have unless we speak about them or act upon them. Hence, those thoughts and whispers do not harm you, Allaah willing.
Finally, you seem to be suffering from obsessive whispers, so we advise you to repel and ignore them because getting carried away with them leads to great evil. You should do your best to be obedient to Allaah and perform good deeds, as good deeds wipe out the bad deeds.
Allaah Knows best.