I asked many doctors about it online but no one address me about the exact cause actually I have whitestrech marks on my butt which is fine I am not bothering about it but my main concern is about the severe darkness on some areas of my butt some r more darker nd some light nd I am facing this problem from many years becoz it does not match to my real complexion I hope you find out the root cause nd also suggest me some lightening creams is it biluma cream good or not becoz it s not a problem of melasma or not like common hyperpigmentation can you contact me on whatsapp.