Feedback and praise can help build confidence. Your supervisors could be the best people to boost you before your viva. You have to pick your questions to be as helpful to you as possible.
Don’t ask them how you could be better. Don’t ask them about how your work could be improved. Don’t ask them to critique your thesis.
Ask them to describe your qualities and talents. Ask them to describe your successes. Ask them why these things matter.
Ask them questions that are more likely to build you up, rather than give you more to obsess over. There’s a time and a place for constructive criticism. I don’t think that time or place is the weeks leading up to your viva.