From the symptoms since the rash has been present for such a long time, it can be due to dermatitis, eczema or psoriasis. Hives was a possibility had it come and disappeared, but since it is persistent so it is less likely. Psoriasis is a long-term (chronic) skin problem that causes skin cells to grow too quickly, resulting in thick, white, silvery, or red patches of skin.It is thought that psoriasis occurs when the immune system overreacts, causing inflammation and flaking of skin.
I suggest you to get it evaluated from a dermatologist and get the diagnosis confirmed.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.