Hi Paddy,
I have EXACTLY the same problem as you do!, I have been and had a swab taken and had a urine sample tested but both came back negative!, My Doctor is being VERY nonchalant about the whole thing, HE says it is due to my age and the fact that I am on HRT and have had a histerectomy....he has mentioned that it is down to Estrogen levels......THATS ALL VERY WELL....but I am still suffering! I have been taking Clarityn tablets to aleviate the Itching symptoms but I am as uncomfortable as you by the sounds of it....talk to your other half, I did you may be suprised at the support you receive...also go and see your GP it maybe that you have the same as me.....it certainly sounds that way.
Whatever happens good luck.