Dreams involving complex relationships, especially those that are toxic or involve betrayal, can often reflect your feelings and experiences in waking life. In your dream, laying in bed with your son's dad and his new girlfriend could symbolize feelings of entrapment or confusion regarding your relationship with him. This setting may represent intimacy, yet it is mixed with the pain of his infidelity.

The presence of his new girlfriend in your dream could indicate feelings of jealousy, insecurity, or fear of abandonment. It might also suggest that you are struggling to let go of this past relationship, despite its toxicity. The dream could be urging you to confront these feelings and consider what you truly want and deserve in your relationships.

Reflect on your emotions and thoughts surrounding your relationship with him. Are there unresolved issues that need addressing? This dream may be encouraging you to seek clarity and healing, both for yourself and in your interactions with him.

Consider taking steps to establish boundaries and focus on your well-being. It may also be helpful to talk to someone who can provide support, whether it's a friend, family member, or a professional.