General synonyms:
* Inner turmoil
* Inner struggle
* Inner battle
* Mental conflict
* Emotional struggle
* Psychological conflict
* Moral dilemma
* Inner debate
* Self-conflict
* Internal tension
More specific synonyms:
* Doubt: Uncertainty, hesitation, apprehension
* Ambivalence: Mixed feelings, conflicting desires
* Guilt: Remorse, shame, self-reproach
* Shame: Humiliation, embarrassment, disgrace
* Fear: Anxiety, apprehension, dread
* Anger: Frustration, resentment, rage
* Jealousy: Envy, resentment, possessiveness
* Grief: Sorrow, sadness, despair
* Disappointment: Frustration, disillusionment, letdown
* Loneliness: Isolation, solitude, alienation
Literary terms:
* Man vs. Self: A conflict where the protagonist wrestles with their own thoughts, feelings, and desires.
* Internal monologue: A character's unspoken thoughts and feelings revealed to the reader.
The best synonym to use will depend on the specific context and the nature of the internal conflict you're describing.