Dry skin? Have you started using a new soap, new laundry detergent, or recently bought some new bras? If something like that has changed, it could be irritating your skin.
Try using a mild, unscented lotion after each shower. Avoid soap on the itchy areas. For the lotion, go with something like Aveeno or Eucerin.
Speaking of Aveeno, the bath powder you soak in is very effective. If these measures don’t help, or you develop any other symptoms like a rash, talk to your doctor.
If you suspect it could be an allergic reaction to something, or you start to get hives, take some benedryl and use a process of elimination to figure out what caused it.