Hi there ~
I understand your concerns. I believe that the rash
on the head of your penis needs medical attention. If it is not an STI as was diagnosed by the doctor, you are being treated for epididymitis
and I recommend that you continue your treatment for that condition. I wonder if an HSV
titre was run on the list of STIs tested as the rash very much from your description resembles that. If you are not having any relief from the medications and you persist on having the infection please consult a dermatologist
to get the appropriate treatment.
I hope this helps. Take care and have a lovely day!