Oh dear, poor thing.
I had bad rashes and itch around week 26 and it went on for about 4 weeks. I'm not sure if mine is also PUPPS, but i have itchy abdomen and in the night it's difficult to sleep. When I manage to fall asleep i'll end up scratching and bleeding.
keep your body cool - i resort to using aircon often. heat will make you more itchy.
dry sweat off your body regularly - keep a towel with you often. Sweat retention will cause rashes, and then scratching.
i also used lotion/oil (clarins tonic oil) daily after my showers to help my body stretch without itching. do not use calamine lotion. i think it will dry the body.
drink lots of fluid to help your body stay hydrated
if you also scratch when you sleep, consider wearing mittens/gloves. I wore them so that i dont end up bleeding when i scratch in my sleep.
If your itch does not stop, i think seeing a specialist may help. They have medicine to help you.
All the best.