Itchiness in pubic hair, pregnant, red patches, dry skin. Urine, blood tests normal. Causes?

i have itchiness on the pubic hair which i believe occurs days after i shaved. it always itchy around night time. it has been 3 days, it doesn t go off and i m worry. i have not apply anything because i m 4 months pregnant. no smell or leakages, just coin-sized red patch which shades off flakes or dry skins. my urine and blood tests does not detect any anomalies. what is it anyway? herpes or psoriasis? if it sounds dangerous, i m going to the hospital today. if it completely harmless to my baby, i ll just wait till my coming appointment which is this Friday. thank you.