Hi,
Noted your short history
severe itching below
umbilicus to pubic bone area without any rash or so, increases at night when laying on back, laying on stomach reduced it but then feels hot.
If there is no rash then obviously the cause looks to be related to nervous system.
Or it is possible that you are developing
herpes or so.
Nerve pinching can cause the same problems.
Or developing
scabies wherein the rash may appear within few days.
This is atypical hence I would advise you to consult your Doctor for clinical evaluation, examination and may be reference to a Specialist like
Dermatologist or so as per his findings.
This may give a clue and get your proper management.
Till then stop using any soaps.
Do not use underwear with elastic as chemical in this elastic can cause severe itching without any visible rash or so.
Avoid hot and humid atmosphere.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. T Chandrakant, ENT & General Surgeon