Terrified!! Breast indent when raising arms..

A few days ago when I raised my arms to pin my hair up I noticed a large indent underneath my left breast. I do feel for lumps when I’m in the shower but never usually take any notice in the mirror. The indent only shows when I’m raising my arms and is underneath my breast on the inside. No idea how long it’s been there. I’ve lost a stone and a half in the last 3 months and I am wondering if being a bit fatter maybe disguised the indent? Anyway, when I saw it initially I hoped I’d been sitting in a position where my bra may have dug in and that it would just disappear. It hasn’t and the more I look at it in the mirror the worse it looks. I have a GP appointment booked for tomorrow but I am absolutely worried sick. I’m 42 and have large (36G) and extremely far from perky breasts and feel so embarrassed already about having to bare all to the Doctor but I’m also thinking because they’re so big it might make it harder to detect anything? Doctor Google has absolutely scared me to death as everything l have seen so far implies an indent is a sign of advanced and aggressive cancer. I’ve spent all day today crying and convincing myself it’s going to be the worst case scenario. I’m not sure why I’m posting in here as I know that without any examinations or tests there are no definitive answers but I don’t have anybody else to talk to. Any positive stories would be good.

Thank you for taking time to read this,

Emma