Lauren, dreaming about your recent ex getting together with the girl he cheated on you with is a powerful symbol that reflects the unresolved emotions and trauma surrounding this relationship. This dream indicates that you are still processing the betrayal and the hurt that came with it, which is evident from your lingering feelings of love towards him. The presence of the girl he cheated on you with in your dream signifies your feelings of inadequacy and comparison, which can often stem from such a painful experience.
Your waking up anxious suggests that this dream is tapping into deep-seated fears and insecurities. These emotions may be more intense due to your frequent stress and anxiety. The fact that you still love him, despite the betrayal, highlights the internal conflict you're experiencing. This is not uncommon for someone who has gone through traumatic relationship difficulties. The dream serves as a mirror to your current state of mind, reflecting the unresolved pain and the struggle to move on.
Given your background of substance abuse and traumatic experiences, this dream might also be a manifestation of your subconscious attempting to reconcile past hurts with your current emotional state. The anxiety you feel upon waking could be a direct result of your mind trying to process these complex emotions while you sleep. The dream can be seen as your psyche's way of bringing these issues to the surface, urging you to address them consciously.
Your frequent sadness and the lack of joyful activities in your life might be contributing to the intensity of this dream.