Is the period in which the hijab was not completed considered "what is in the self" (a thought/inclination), and is that considered shirk that nullifies deeds?

What you are experiencing has no relation to shirk (polytheism) or the nullification of good deeds, and repeatedly asking about it may strengthen the waswas (whispers/obsessions). Therefore, be diligent in the remembrance of Allah, observe the obligatory duties, and avoid sins. Obedience to parents regarding the hijab is obligatory, for whoever seeks Allah's pleasure despite people's displeasure, Allah will spare him the trouble of people. The hijab does not require a specific garment or color; any attire that meets the conditions of lawful dress is considered hijab according to Sharia. Regarding covering the face, there is a difference of opinion among jurists, and the most preponderant view is that it is obligatory. However, it is permissible to take a concession when there is a need, by adopting the view of those who hold it is not obligatory.