Small stain found in bra - 29

Hello,

On Monday I went to my doctor because of a small lump I felt. My period is due soon and she did an exam but said she couldn't feel anything. I've noticed that the lump has started to go down the closer to my period. She suggested I come back after a couple of cycles to see if the lump was still there but she said she wasn't worried and my lymph nodes etc were normal. I do have one member of my family who has had breast cancer which is my grandmother on my dads side but that was in her 70s and I've been told that it doesn't raise my risk above average.

A couple of days ago I noticed a very small oil like stain on the inside of my bra on the breast I noticed a small lump on. I've never seen any discharge from my nipples and I'm not even sure this stain was caused by discharge (or me being an idiot and throwing food down myself) but I rang the doctor anyway and she suggested to come back sooner. I kept photographs of the stain so I could show them and I'm checking my bra daily for any new stains and so far nothing. I also haven't seen any crusting or similar and nothing when I squeeze the nipples.

For those who have had discharge was it a persistent thing? How big are the stains you usually get? I don't really know what to look out for! 

I have poor health anxiety as it is and I know every situation is different but I'm just a bit scared! I know I'm doing all I can but it doesn't feel like enough in some ways!