I must say, I am currently 39 weeks pregnant and am completely miserable from puppps! How did I get it?

Fetomaternal cell tr. Fetomatenal cell traffic through the placenta likely is responsible for puppps. That means that your rash is likely an immune reaction to your baby's cells crossing your placenta and lodging in your skin. It should all improve rapidly postpartum. If you are indeed 39 weeks, ask your obstetrician to deliver you!