is viral infection caused by varicella zoster virus
According to the symptoms told by you there are two possibilities,
1. as chicken pox involves the mucocutaneous membrane it will affect the external genitalia also,
2. because of itching due to blisters you may scratched that area leading to cellulitis
I suppose along with above tablets you may also taking antiviral
Now you have to visit your doctor again and get examined. If super-added bacterial infection is there they will prescribe antibiotics also.
If not they can make out the actual cause by examination.