20s with sensitive skin, how to lighten darkness under my butt? (Photos)

I am in my 20s with sensitive skin. I've had this darkness under my butt for as long as I remember. It's kinda like a birthmark. I have tried scrubs, lightening oils, and serums and a bunch of other stuff that hasn't worked. I am wondering if there any way that I could get this skin to match the surrounding areas of my bottom. Would this be like a birthmark removal, laser used for tattoos...?