What Causes Painful Pus Filled Acne On Left Side Of Vulva?

Hi
I am a 27-year-old girl and have not had any sexual relationship to date. For nearly three years I have had a painful acne-like thing on the left side of my vulva close to the joint of my thigh. It preiodically(once in a month) grows large, filled with some pus-like liquid and gets vey painful. Till to the end of its 2week life some of the pus comes out, but not completely as it looks like distinct from the other part of skin by a darker skin and raised surroundings. In 2 weeks on the average, it gradually gets smaller and less painful. But a slight pain is remained whch is sometimes impulsive too. Exactly at its opposite side on the left side, there is a similar dark area which I am afraid to turn into this one.



I didn't realized any timing relation to my period. But I have some erotism feelings and by mistake made my sexual senses arouse(and repeated for about a one and a half year). It's near a year I have left the habit but guess it must have causesd some hormone imbalance in my body.



Sometimes have pains in my belly.



Please help me. I want to know if there is a recognized problem in medical sense or just some description unique to me.