Mama, please check with your OB or go to your health center asap, itching during pregnancy, especially with rashes, needs proper checking kasi maraming possible causes at alam nila kung ano talaga ang problema mo. Hindi ko mapapantayan ang doctor dito, sorry!
In the meantime, try to keep the area clean and cool, pero go see your doctor talaga, they'll know what to do. Sending you strength, hopefully it's something simple lang!