Thanks for writing in.
The condition you are suffering from can be intertrigo,contact dermatitis
As there is itching the chances of STD are very rare.
It can be hair follicle infection
or friction dermatitis
Sexually acquired infection would present earlier and will have pain rather than itching.
Consider visiting your GP or dermatologist
for proper diagnosis and treatment.
You can take tab.Zyrtec for itching till you visit a doctor.
Hope this helps.