Boob acne?!?

So I'm not pregnant, at least I haven't had a blazing positive or anything. I stopped tracking so have no idea where I am in my cycle. I had a few faint lines but chopped it up to indents because well it's so hard to tell. Anyways, I noticed this boob acne. I have never had this?! Does stress cause this?? What else could cause it? I'm not using any new bath soap or shampoo or anything and am washing the same. Pic to show you lol sorry girls.