OK. Now for real. There are a couple of options. You could:
1. use a thickening shampoo/conditioner (they are not THAT good though).
2. Try nizoral shampoo.
3. Use Paul Mitchell intensive conditioner: it always makes my curly hair look very thick and luxurious.
4. get hair implants (last resort).
Perhaps you should sample around with the different hair products. You could go and see your doctor as well because he could give you the prescription-strength nizoral products and perhaps other suggestions as well.
good luck.
bunny