I have this rash on my lower back. its very dry and j dont know how it appeared. its red and blotchy and dry?

Most localized rashes represent a local contact with a triggering agent. However, most rashes are rather non- specific and can only be correctly analyzed by a direct visual exam.

This could be from a number of many skin diseases. Eczema, psoriasis, bacterial or fungal and even viral. Best see a dermatologist as soon as possible for determination of the kind of rash and treatment.