Is a person considered unfaithful to God if they experience an inner feeling of being special or among the righteous when doing good for others, even while striving to resist these thoughts?

As long as you intend the Face of Allah with your deeds, you are sincere. You will not be harmed by any whispers, joy in your deeds, or self-admiration that may cross your mind, as long as you do not succumb to these matters and strive to repel them, and remind yourself of Allah's grace, His immense favor, and the shortcomings and weakness of humanity.