Headache and nausea are side effects of head injury you had.

Have you been examined after the accident?

I fell back in July really hard on a cement garage floor and hit the back of my head, I hit so hard I hit it again. I have had sever headaches every since. Plus my neck gets hard to move. Can there be anything major wrong. No I have not went to the doctor

You need to go to the doctor after any head injury where you have symptoms afterward. This is not something to ignore. You may have even cracked a vertebrae in your neck, which could be putting pressure on your spinal chord. You could have cracked your skull. You may have swelling in your brain. You don't know.

I would go to the hospital now, not the doctor. Don't hesitate!

I don't mean to scare you, but this could be really really serious.