I have drinking OJ and Vitamin C enriched fruit juice. I go to a chiropractor once a month. When I sprained my shoulder I went twice in that week. I pretty much try everything. From herbal remedies to massages to pain pills.
I would see a chiropractor, you said you sprained your shoulder, well, if you did that, then other problems could very well arise in the region of your neck. If vertebrae or "out" you will get the dizziness you are describing, a few treatments and you should be a lot better.
Also, add a good food grade multi vitamin and mineral to your diet, these will provide the needed electrolytes and other nutrients you may be lacking.
If you like bananas and orange juice, try to eat those and drink OJ at least once a day and see what happens. Your potassium levels may be low which can cause the dizziness and headaches. The OJ will provide the Vitamin C that we need as well. I hope this helps. Also, you may want to request a MRI just to be on the safe side.