I agree with the post about the glands. I had one and it left a little scar in the gland. It is a pea sized bump. It doesn't hurt or anything. At the doctor, he said the same thing I suspected.
The thing with zits, is you usually have more than one and they are usually a little more near the surface. You can pop them as they come to a head, usually a white head. The herpes doesn't come to a head, but will crust over like a fever blister, is hardly ever just one lesion, again are painful but are still in the upper most layers of skin.
I would suspect the clogged or abscessed gland or a sebacous cyst, or abscessed hair follicle. Leaning on the gland hypothesis. The cyst or gland feel "deeper". The oil gland cyst (sebacious) cyst and the other gland also hurt beyond belief, rarely form a head or can be popped. Both glands can be incised and drained.
I would suspect that since you are constantly having a re-occurance, I would go to the OB-gyn. I would have it incised and drained and cultured. And take action accordingly.
Mine started out with what I thought was a boil. Couldn't be popped. Then went away. But left a pea sized knot where it was. The last time I had an exam, I had the doctor check it out, and he said it was just scarring where the little infection had been in the gland. There was nothing to do as it was not infected at the time. And I have not had any problems since.
I would definatley have it checked out only because it is re-occuring and needs to be assessed by the doctor. Could be something easily treatable also, and then there would be no need to suffer at all.
Good luck,
L.