The skin above my upper lip has darkened like a mustache w/o hair: why? How can I fix it? I'm really self-conscious about it.

Likely melasma. You are describing melasma, although i cannot be 100% certain without proper evaluation. Associated with hormones (pregnancy, birth control) and 100% sun. You must wear sunscreen with > 5% zinc oxide and or titanium dioxide and reapply throughout the day. Avoid heat on face directly, too. Many bleaching creams work well with the sun protection. I get great results with obagi nuderm system.