Itchy armpits - nursing mummy

Hello ladies!

My Lo is 6 months now and I’ve been pumping and breastfeeding this whole time. I noticed during my third trimester that my armpits became dark and a tiny bit itchy. After I had my baby my armpits have been so damn itchy... it comes out of nowhere and it’s like I was bitten by a ton of mosquitos or something. So I went to the dermatologist today, he diagnosed me with dermatitis and he gave me steroid cream, which so far doesn’t really seem to be working. I feel like the itch is really under the skin, like IN my armpit. Anyone experienced this?