Hi, thanks for asking from HCM.
I can understand your concern. You are suffering from fever with rashes. It could be du etc
: Pyoderma or 
skin infection due to bacteria - It usually presents as multiple rashes, pustules, fluid filled vesicles over body along with fever.
: Viral fever like chickenpox, Measles can cause rashes over body with fever
: Some times 
drug allergy or 
allergic dermatitis with secondary infection can present like that.
The bump behind ear and neck nodes are most probably "lymph nodes". it got enlarged due to skin infection and inflammation.
You must 
consult dermatologist and get yourself checked for management. The doctor will examine you and advise
: complete blood count
: lesion fluid culture and sensitivity
: Antibody test against chickenpox if suspecting it
: If diagnosis not clear and disease is getting worse, then 
lymph node biopsy to confirm it.
Further treatment will be decided after confirmation. It is medical management only.
Hope it will help you. If you get blood reports, you can ask me. I will guide you about the treatment.
Thanks. Take care.
Dr Ishu Bishnoi