What does it mean to get pimples on your vagina? it seems like every period and tight underwear how can i fix it? they hurt bad

Many reasons: Tight underwear is a problem wear cotton underwear or leave open to air when possible. Sweat amd infection in the hair follicles most likely. Do you shave your pubic hair. If so = stop!

Vulvar Folliculitis: Vulvar folliculitis inflammation of the vulva due to a staphylococcal infection of the pubic hair follicles. The inflammation can be a result of shaving or waxing the pubic hair or tight underwear and presents as an itchy and tender condition. Treatment generally involves a topical or oral antibiotic.