Itchy and scars under breasts

Emi

The under part of my breasts have been itcht and I'm not sure what it is. I figured that it could be a heat rash because i sweat alot and my bras arent the best for comfort or support but my boobs starts to scar and this is the third time it happened. My mom says its a rash, but my friends and bf worrys that its breast cancer. I

Should i tell my doctor about this and have her check? Im very concerned.