I have 2 lines/creases on my stomach and they WONT go away!!?

Ok so i have these 2 lines/crease on my stomach (both above my belly button and a little far apart from eachother) and i think they formed from my stomach flab overlapping eachother. I noticed that when i sit down with my back bent, it gets darker and darker. I tried sitting straight for a week and it did grow a lot lighter but you can still clearly see the lines! somebody please help, if you know ways to atleast make them unseen such as putting something on them, please share!