Muhammad(sa) was in doubt about his own Prophethood and about the Holy Quran being the Word of God, as is evident from this verse of Surah Al-Baqarah and Surah Al-An‘am:
This shows that in his heart of hearts he knew that he was not a Messenger of God. Had he been one, or had he shown any miracles, or had the Mi‘raj been a reality, or had the Quran been revealed to him by Gabriel, he would never have been in doubt about his own Prophethood. This proves that he was in doubt about the Holy Quran and his own Prophethood. Hence he is not a Prophet of God.
1 …be not therefore of those who doubt.—Al-Baqarah, 2:148; Al- An‘am, 6:115 [Publishers]