Dreams often reflect our subconscious thoughts and feelings, particularly regarding relationships and choices we face. In your dream, the act of going back to an ex who only wanted you for sex may symbolize feelings of temptation or regret about past decisions.
Seeing the lip gloss could represent your self-image or the way you present yourself to the world. It might suggest a desire to reclaim your identity or femininity in the context of relationships. The realization of making a mistake in the dream indicates self-awareness and a desire for a more fulfilling and respectful relationship, which you seem to find with your previous boyfriend.
This dream could be urging you to reflect on what you truly want in a partner and to recognize the importance of being in a relationship where you feel valued and respected. It might also be a reminder to trust your instincts and make choices that align with your self-worth. Consider how these reflections relate to your current feelings and decisions in your waking life.