Good afternoon. I am hopeful that I will be able to help you today. It sounds like this dream really resonated with you.
While I was reading your question, a few things came to my mind. It may feel that you are not in complete control of your life right now. You ex-husband's presence in the dream may suggest that you are currently finding yourself in a situation that you don't want to re-experience. You may be subconsciously repeating old patterns from that relationship, in your new one. In our dreams, we are much more likely to act out anxieties and fears than we are other emotions. It is our way of working through these in a safe manner. The significance of the back seat is what made me think that you felt in less control, or even "unheard." You may be experiencing a feeling right now that your feelings are invalidated by your relationship. You may want to consider if you are having your emotional needs met- if you feel valued, important, appreciated, secure.
You arrived at "home" but I think this is more of a metaphor for security. His falling asleep is more a reflection of feeling that he was not seeing the problems in your relationship- he was aloof to your needs.
To me, overall, it sounds as though if in your dream you were working through the emotions associated with possibly repeating the same patterns that happened with your ex-husband. You don't want to feel that you are in the same type of relationship, but right now you may feel that your feelings "take a backseat" to someone else's. You may want to consider how you can assert your feelings with either a current partner, or just make sure you feel secure in doing so in future relationships :)
I hope that this has been helpful. Please provide any additional information if you would like!
Thank you! Julie