Hello,
From the symptoms it can be folliculitis, contact dermatitis, sweat dermatitis, heat rash, bites or hives. Take some antihistaminic like Benadryl and apply some calamine lotion on the rash. If the symptoms are worse then please apply steroid creams after consulting a dermatologist. Also wear cotton clothes and try keeping the skin sweat free.
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 dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
The itchyness can be an allergic reaction to soap or shampoo. In bed, in the quiet of the night, you would notice the itch more.