This is hard to treat, but the best treatment available is TriLuma, which is available by prescription. It's important as well to use a sunscreen that provides but UVA and UVB protection, though no block will block all rays, and any rays that get through will darken the lip. I know that this condition is often blamed on hormones, but there is often no correlation either way (that is, stopping the pill may not make you better, nor will getting pregnant make you worse.) I suggest you stop the 8% hydroquinone, which is too strong.
Best.
Dr. Rockoff