alicengls,
I have the same situation as you around 26w. I went to see 5 doctors (3 O&G, one family doctor and one skin specialist). The skin specialist doctor said it might be related to the pregnancy hormones and it is quite common for pregnant women from 24w onwards.
(1) She asked me not to use the normal liquid soap for bathing, she gave me a bottle of liquid and asked me to use it like liquid soap.
(2) She also gave me some cream to be applied to the tummy.
(3) She reminded me not to use too hot water when taking bath.
(4) She asked me to try to stay in dry area like indoor with air conditioning.
(5) To wear 100% cotton underwear.
(6) Stop using the pregnancy scretch cream.
After one week, my situation improves a lot and I can sleep well at night now.
She said once the situation has been improved, I could apply olive oil instead of the pregnancy scretch cream on tummy.