If you are still having the problem, you need to get back to your doctor for a possible referral to the urologist.
I had a swab with a cotton bud in my area, but came back all clear as well :/
If you have not been tested for fungal problems, it may be a good idea to have this done.
Make an appointment to see your doctor so that he can take a swab from the area and get than analysed.
If it is a fungal problem, you will be prescribed with the appropriate antifungal medication.
The doctor may request a further investigation and a referral to a urologist.
Let me know how you get on.
Best wishes.