Itching

Shanice • 27,pregnant with 2nd child
I'm 31+4 weeks pregnant and u have uncontrollable itching only when I'm trying to settle down to sleep.Im fine all day long no itching,but as soon as I'm laying down at night to sleep i can't stop itching..I've gotten up taken showers,lotioned down really good,changed my sheets,flipped my mattress,sprayed it down but nothing works.What could this be?