Itch on my thighs

I’m 28 weeks now and I had this itchy red patches on my thighs since 2nd tri.. I went to see dermatologist and she prescribed me 0.1% steroid cream and moisturiser. I’ve applied for 2 weeks but it didn’t help much and got worse.. Luckily my tummy doesn’t have any rashes. It’s just my legs. I’ve tried calamine lotion, it helps to suppress the itch but i’ll still feel itchy a few hours later. I can’t stop scratching! :’( anyone know what is this?