self-doubt

OXFORD DICTIONARY

self-doubt, n. lack of confidence in oneself, one's abilities, etc.

THESAURUS

self-doubt

Pyrrhonism, apprehension, diffidence, distrust, distrustfulness, doubt, doubtfulness, dubiety, dubiousness, half-belief, lack of self-confidence, lack of self-reliance, leeriness, misdoubt, misgiving, mistrust, mistrustfulness, question, scruple, scrupulousness, self-depreciation, self-detraction, self-distrust, self-effacement, shadow of doubt, skepticalness, skepticism, suspicion, suspiciousness, total skepticism, uncertainty, wariness, weak ego