I'm sorry you're in such a difficult situation, Nancy.
However, your dream(s) reveal some hope and change could come soon. The two train tracks, on both sides of you, indicate that you're feeling you're not making progress like the rest of the world. You're not moving towards your goals as you want to be.
Well, you probably won't be taking the same "track" as most ordinary people. But you *will* make slow and steady progress to your goal (symbolized by walking). The bridge is a good symbol that points to an important decision or change in your life. But it changes in your dream to rocks.
Tell us more about the rocks. Were they obstacles? Loose rocks? Sturdy? Was the bridge made of rock?
If the bridge was made of rock, your decision will have a solid foundation. It will be a good decision.
You need to move forward to a place where you will not feel so isolated (symbolized by the city). Perhaps you can meet new people at school or work?
That the rest of the dream was in the dark only indicates that there are unknowns in your waking life scenario. You don't know what to expect but you are open to new information. You aren't sure who is in your future but you fear no one will be there for you.
It's always scary to make major life changes. Your dreams show you that you have the courage.