Painful sweat rash

I have gotten this painful what I call sweat rash at the crease of my things and vagina. It usually happens when I sweat a lot but right now I live in 30 degree weather. I’m not sure what to do anymore it comes out of nowhere and can be extremely painful. I need help. Does anyone know what it is? I have pcos. I trim regularly and wear cotton panties and scrubs daily. I sleep nude to air everything out hoping it helps. I’m not sure what to do anymore. Does anyone have any suggestions?