Some Advice Please 😔

Ouch, suggestions please! I am 19wks 4days  pregnant and my bust has gone up from a C to and E cup. What with sleeping on my side and not being able to let the skin between them breathe, I have developed a really sore red rash line between my boobs. It's agony. Have tried calamine lotion, sudocrem and also some natural organic mum/baby cream but I think I need something stronger as the skin started to crack on the weekend.
I will go to the chemist but if any of you busty ladies have any advice on what you use I'd be really grateful.Â