What Causes Pimple Like Bumps On Chest?

Hi im an 18 year old girl and for about 3 years now I've had bumps on my chest (3 to be specific) they could be described as pimples at first glance but they aren't. They've never gone away. They don't hurt. Kind of soft at the touch and only itch most times. Color usually blends in with skin color if not pinkish/reddish color. Help is appreciated.