It sounds like a reaction to maybe your underwear/clothes or like someone else said, pads?
i too have this problem and my doctor told me it's partially due to a reaction to sanitary napkins (Always being the worst reaction i've ever had) and partially due to the chemicals used to whiten toilet paper. the tissue breaks down and parts are left behind, i have since stopped using Always and i only use Charmin toilet paper... but that's just me, you have to see what works for you and what doesn't...
Do a search on hidradenitis suppurativa, to see if the symptoms resonate with you :-)
A friend on mine has had a problem with ingrown hairs and has explained it just as you did. Maybe thats the problem that you have. just an idea.
What does your gynecologist say? Surely if the problem is that bad and has been going on for so long, you've been to the doctor. If your doctor doesn't know, see a dermatologist or another gyn, too.