Is the word "I hate it" — in the context of the situation mentioned — considered mockery of God? And does mockery occur with such a statement?

The questioner's mind will not find peace except by ignoring the whispers (waswas), consulting psychiatrists, striving in supplication (dua'), and using legitimate ruqyah (incantations). Repentance is obligatory for all sins. The Prophet, peace and blessings be upon him, used to seek forgiveness for all sins, and this was a teaching for his Ummah. It is desirable to seek forgiveness and repent for what one knows and what one does not know, as mentioned in the supplications of the Prophet, peace and blessings be upon him.