There's a picture of the rash.
I've been pulling up all kinds of pictures of different rashes but none seem to match up.
It can be due to allergic reaction, scabies or heat rash( less likely). If it is painful then herpes is an important possibility. Scabies is a contagious skin infection caused by a parasite – the mite, which burrows under the host’s skin and causes intense allergic itching. It is transmitted from objects or beddings, but more with direct skin- to – skin contact.
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.