(Kinda TMI) What is on my boob and back??

This started appearing soon (I assume) after first taking the pill. They're dark patches of skin that aren't irritated, itchy, raised or anything like that- I wouldn't have known I had it all over my back until my boyfriend mentioned it. Has anyone had anything like this? The closest think I can find is something called melasma but my skin hasn't been in the sun and it's not on my face at all. Thanks!