What Could The Discolored Spots On Skin That Feel Numb Be?

Hi, im a 21 year old female and i've found three pea sized spots on my skin that are a slightly different color then my skin and they're numb. they're not hard lumps they're just like the rest of my skin only a little tanner in color. one spot is on my back and the other two are on my thigh and chest. i've also noticed that theres no hair at all growing on these spots. any ideas what it could be? i first found these spots a few years ago.