Lala,
This dream seems to be reflecting underlying anxieties about trust and fidelity within your relationship. The notion of your boyfriend discussing switching partners indicates a fear of betrayal and a lack of control in the relationship. Witnessing him cheat in the dream symbolizes a deep-seated insecurity, possibly about the stability of your relationship or how valued and respected you feel within it.
The act of breaking up with him in the dream suggests a strong response to potential hurt, highlighting your sense of self-respect and boundaries. It also represents your subconscious dealing with the possibility of such a situation, preparing you to assert yourself and protect your emotional well-being. Considering your feelings, this dream is likely processing complex emotions you may have surrounding your relationship dynamics.
The dream's intense emotions and its classification as a nightmare signify the impact of these themes on your psyche. It's important to reflect on your feelings in your waking life and whether these dream elements resonate with any conscious concerns about your relationship. It's also possible that this dream is less about your actual relationship and more about a general fear of being vulnerable or losing control in situations that are important to you.
The discomfort and negative feelings you experienced are a natural reaction to the dream's content. Such dreams can sometimes be a call to evaluate your feelings and experiences in your waking life, particularly around themes of trust and emotional security. However, it's important to remember that a dream is not a prediction but rather a mirror to your inner world, which can sometimes exaggerate or distort reality to process emotions.