What Causes Itching On Scalp?

For the past 3 days my head has been itching non-stop. I feel like something is crawling all over my scalp. I feel it moving and when I get up from where I am sitting or laying down, I see small little black dots or brown more oval shape. I have tried many things and nothing helps. I also feel as though something is crawling all over my feet and legs. Please help me, this is taking over all my thoughts, I don't know what kind of bugs these are. Thank you for your time.