My hair is very dry and even the density is low what should i do?

Dry and Thin Hair : Beauty salons revel in a panoply of products that purport to add body and moisture to your hair, but you want to be sure that you don't have an underlying dermatologic condition, marginal diet, or certain systemic disorders such as lupus or scleroderma. If this issue with your hair represents a new change, and you seem to be losing hair, it is best to consult with your doctor.

Get thyroid checked.: Dry thinning hair is a sign of hypothyroidism, as is lethargy and weight gain. If you have some of these other symptoms, or even if you don't, you should get your thyroid levels checked out. If this is ok, and you're in otherwise good health, look into shampoos, etc. That help thinning hair. Best of luck.