What could be the possibility behind discolored lips? Originally normal until I got older, now they are pink & black. (photo)

I noticed the issue in high school in the corners of my mouth. I realized it came from licking. When I stopped my normal color returned. Now it is on all of my lips along with very dry dead dark skin. I exfoliate with sugar and water every kow and then to remove the dead dark skin but it's a hard battle to fight and I lick a lot without noticing. It gets really dark where the pink pigment stops. Like a dark line. What are some options to get my lips back to their healthy vibrant color?