If you have patches of pigmentation you will need to use a chemical or laser treatment for it. Various bleaching agents are available OTC, but I would suggest a dermatological opinion and prescription medicine.
Tretinoin mixed with hydroquinone works well. For at-home lightening, mix hydrogen peroxide 20 volume in a bit of powdered skimmed milk and apply the paste on effected areas.
Use a sun block lotion or cream with a SPF of 60 and DO NOT USE STEROIDS.
Avoid being worried and/or sad. And check for any melasma causing drugs you may be using e.g Oral contraceptives etc.
Hope your condition will improve with the suggestions. Take care.