Hi Joel136,
Well your description makes it sound like a fungus because of the itching but then later you mention bad pain the first two weeks and that sounds like something else. Herpes hurts a whole lot. You are lucky that the herpes test were negative most people by the time they are adults are positive for at least herpes type 1 IgG cold sore. That would have showed up in the blood test. Did you get checked for all the STD's? Chlamydia, Gonorrhea, Trichomonas, Syphilis, etc. Also, STI's Ureaplasma urealyticum and Mycoplasma genitalium and maybe some other species? All can cause symptoms of genital pain and or not. Sometimes they don't and sometimes they linger. Usually, things that just itch are fungal (either something like joch itch or a yeast). Have you tried any thing that has terbinafine (Lamisil)? That works better than the other antifungal creams because sometimes the fungi are resistant to the other ones. This is over the counter and yes you can use it in the genital area not just on the feet etc. It takes about a solid week or two to go away and use it several times a day (whatever the package inserts say in the medication). Usually, joch itch has an itcy burning feeling. If this doesn't help then I would see a dermatologist to see what exactly it is. They can help you get the right medication if it is psoriasis. It is not likely to have it in that area alone.
mkh9