Thanks for writing in.
Darkening of skin is caused by sunexposure and hormonal
Excess weight and MSH stimulation can cause darkening of skin.
Chemical peeling can give you fast and long lasting results.They are available at dermatology clinics.
Apply cosglo cream at night.Take vitamin C
You can use gel based sunscreen like Zoray acquagel sunscreen.It wont make you look dark.
Hope this helps.