What Causes Skin Cracks And Itching On The Butt Crack?

I've been having some butt crack issues. Before, the main top of it would always be itchy, but when I scratched it, it would be like a ton of dead skin cells. Yet, it doesnt stop there when I would be in the shower or using the toilet, if I bent down the skin would tear and bleed. But it wouldnt be like a huge tear. Anyway, now I have some sort of rash which itches alot. What could cause this? How could I prevent and treat it?