What Causes Tiny White Pus Filled Bumps Under The Breast?

I have white tiny bumps on and under my breast and when I squeeze them, a thick white substance (similar to a blackhead) comes out. The bumps arent pimples, they look like my pores just with white toothpasty stuff inside. Theyre naked to the human eye but I notice them. I also was disanosed with PCOS so I was wondering if it had any relation? Thanks