Can feel something when I stand up to self exam but not when I lay down??

I found something about 3 months ago- It was not the normal lumpy feel that I have everywhere else. This lump is hard and is about the size of a silver dollar. Its under my right breast at like and angle from the fold of my armpit. It does not seem as if it has gotten any larger or smaller- but I make sure I check it a week before and a week after my period to be on the safe side.  I am only 25 but concerned as I am very admit about getting annual exams and self breast exams.  This spot is not really painful but is does feel tender at times. I have had two aunts with breast cancer-- One was a gene carrier the other was not.

Should I be concerned or just wait it out to see?

I agree, why wait? Definately you need to see a doctor. Good chance it is nothing (80%) but you want to be sure. I could only feel my lump when I laid on my back and put my arm over my head. Mine was only 6mm but I found it and had it checked. Good thing I did. I also had very dense, lumpy breasts so it was hard to feel. I had been checked for other lumps several times and they were benign. Please get it checked out asap.

Hugs, Gail