It seems that you may be having fungal infection
May be tinea cruris
and corporis.Drug rash
is another possibility.
First , antifungal tablets with antihistaminics should be taken.
Anti fungal cream may be applied.
Take three months treatments.
If no response allergy or drug rash may be cosidered.
You should consult the expert dermatologist
I hope you got my answers.
Dr. Ilyas Patel MD