You seem to be suffering from melasma. The treatment of melasma is prolonged and chances of recurrence is quite high after stopping the treatment as has happened in your case. The best way to prevent recurrence is to use mild depigmenting creams in maintenance phase too instead of discontinuing the therapy altogether. You may follow these suggestions to help treat your problem-
Take oral vitamin c
and antioxidant supplements
Use a sunscreen of SPF 50 like melaguard twice in a day even if staying indoors
You may use hydroquinone
based creams, Glycolic acid
creams or Triple combination like skinlite
to reduce pigmentation. To get better results you may take sessions of chemical peels
( Glycolic or TCA) or laser sessions to reduce the pigmentation
Once the pigmentation reduces switch over to milder Kojic acid
arbutin based creams to keep pigmentation at bay( melaglow, kojivit, clearz plus). These creams can be used for prolonged period without harming the skin. You can also take monthly sessions of chemical peels as a maintenance therapy.
Avoidance of sun exposure, use of good sunscreen and a mild pigmentation reducing regime is a key to prevent melasma from recurring after taking treatment. Hope that answers your query. Take care.