I have a recurring - usually once a year - itchy, painful raised rash with small pustules on the same spot on the back of my thigh. it lasts in this form for about a week, then takes another 2-3 weeks to disappear?

Herpes?: Very suspicious for genital herpes due to HSV2. Some genital HSV2 infections recur not directly genital, but nearby: buttocks, thighs, lower abdomen, etc -- anywhere in the area covered by men's boxer shorts. Herpes is especially likely if it starts with red bumps that become blister-like and then sores with scabs. Get care & get tested within 1-2 d of the next event. Or have an HSV blood test.