I slipped and fell down my stairs hit my head and top part of my back. Really bad I am now experiencing some dizziness two days later escspecially when I lay on my back? My head is fine on the outside my neck hurts and my back hurt. What should I do?

See a doctor. You should have done that at the first sign of dizziness.

What should you do...see a doctor.....

I agree with the others. The only option is to see a doctor. You won't get a diagnosis online. Dizziness after a fall is something to be concerned about, and should be seen to by a medical professional, not a bunch of nameless people online.

Good luck.

You could have a concussion or a subarachnoid hemorrhage. Any nausea or vomiting?

In the end, you will most likely need a CT scan to rule out a brain bleed. Please seek emergency medical attention.