How do you handle feelings of self-doubt and self-distrust?

Thank you for this really great question! Questioning our own thoughts and feelings can result from a variety of conditions/circumstances. It may be one aspect of Obsessive-Compulsive Disorder for example. Often, however, it is a byproduct of having experienced repeated invalidation of our experiences. Typically this occurs in childhood when someone is part of a family system that inhibits expression of feelings and thoughts or frequently invalidates the child's experiences by communicating in some way that the child's feelings and thoughts are wrong. For instance, a family member may dismiss the child's feelings or tell the child he/she is too sensitive. In families where there is verbal/emotional abuse, a child may be made fun of or otherwise punished for expressing feelings such as anger, sadness or fear. Often in families where there is alcoholism/addiction, the entire family system often engages in denial, turning a blind eye to the alcoholic's behavior and pretending everything is ok. This is particularly confusing to any family member who sees the "elephant in the living room" and can lead to that person questioning their own experiences. As this continues, the child doubts his/her experiences more and more and looks to others around him/her to determine whether their feelings and perceptions are correct. If their home life is unsafe due to abuse and/or addiction, the child will maintain focus on the abusive person in order to better anticipate a blow up or figure out ways to please that person, (or manage their behavior). Over time, they do not fully develop their own sense of self and struggle to identify their likes/dislikes, values, and opinions. This a defining characteristic of Codependency. Of course there are other types of scenarios that can produce this self-doubting, but invalidation is a common denominator.  Therapy can help shift the focus from seeking validation for one's thoughts/feelings from external factors to identifying and validating your own feelings, thoughts and perceptions. This often involves exploring irrational core beliefs and reframing them in more realistic, "reasonable" terms. Through this process one can begin to develop a sense of who they are, what they think and feel and what they want and need. As you begin to trust your own experiences, the need for external validation decreases. I hope my response has touched on any factors that are related to your particular situation. Best of luck!