Thanks for the query.
If you are having only itching and swelling, that could be allergic reaction
the material of the inner wear or it could be due to some infection.
As you are not having symptoms like discharge, bleeding etc. no need to worry.
Possibly your doctor may wanted to reexamine once or he may wants to take a swab for culture and sensitivity.
So you discuss clearly this time with him to find out the exact nature of the problem and take treatment accordingly.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429