Sore under boob

[angelbump]

Bit wierd but right in the crease under my boob is getting sore almost like friction or something?
Is it my bra (which isn't underwired anymore as I'm a big boobied girl)?
Is it friction or is it because it gets sweaty more now they're bigger (ewwww i know)!?
Anyone else suffer and have any remedies?
Thanks ladies x

 

[CharCharxxx]

I get that sometimes mine goes like a rash for few days then goes. Not pleasant is it lol x