Other than the zombies :-) it does not sound like it was about your actual life now but thoughts and worries you may have had. The ruined building and old school desk, etc. could mean the thoughts and worries have been with you a long time. I usually find a dream dictionary and do some free associating on some of the more discrete symbols like "cave", snow/frozen/whiteness, etc.

If it were my dream I would take comfort from the shaman telling me I would be protected; I would take that to mean I could think about and work on my fears and it would be helpful/all right, that my mind is able to take care of me in that. I think "cave" is about refuge too so that would make me feel my mind/dreaming self/unconscious is trying to help me in my real life: Dream Moods: Your Dream Symbol Interpretation

I believe we are all the people in our dreams and I would look at the "progression" of people in yours, from bullying crowds of unknown people to zombies, to the girl and then her guy, her being alone and then you being alone.