What Could Dark And Saggy Skin In Pubic Area Suggest?

I'm in my early teens and I have some dark,loose skin hanging in my pubic area-around the part on top of my vagina. Plus, it is only this 'dark skin' which is sagging. The thing is that I'm thin (43 kgs). This feels rather uncomfortable (literally), as all this excess skin is there. My pubic area is quite small anyway.