Do something about my hair

My hair is super thin and stringy. I have to wash it every day. If I don’t, it gets really greasy. The thing is that I am sick of having super think hair. I have tried plenty of volumising products, and none seem to be helping. The only thing that works for me is blow-drying my hair with my head down. After I do that my hair is really poofy, but 5 minutes later it’s back to stringy and thin.