Dreams can be quite vivid and often reflect our subconscious thoughts and feelings. In your dream, several elements stand out:

1. Not wearing a bra in public: This could symbolize vulnerability or a feeling of exposure. It might indicate that you are feeling unprotected or exposed in some area of your life, or perhaps you're wrestling with issues of self-esteem and body image.
2. Ex-boyfriend eating you out: This could point to unresolved feelings or desires related to that past relationship. It may also represent intimacy and the complexities of past connections, possibly highlighting a longing for emotional or physical closeness.
3. Running away from your ex and hiding in the bathroom: This suggests a desire to escape from past relationships or situations that may have caused you distress. Hiding in the bathroom can symbolize a need for privacy or a safe space to process your emotions.

Overall, this dream may reflect your feelings about vulnerability, intimacy, and the need to distance yourself from past relationships. Consider reflecting on how these themes play out in your current life and what steps you might want to take to address feelings of exposure or unresolved emotions.