There are various synonyms for "doubt yourself" that can help you express uncertainty in a different way. "Second-guessing" refers to questioning your own decisions and abilities, while "insecurity" signifies a lack of confidence in oneself. "Self-doubt" is another commonly used term for questioning your own ability or tending to underestimate your skills. "Uncertainty" implies not being sure about something, and "hesitation" refers to the act of delaying or pausing before taking action. "Lack of faith" also describes doubting your own abilities or potential. Finally, "apprehension" conveys a feeling of unease or anxiety about a particular situation or one's own abilities.