Actually all the sunscreens work for 3-5 hours only (depending upon exposure to the sun). You will surely get back your original color soon. To be on a safer side, try the below given homoeopathic creams:
cream (Biovalley) apply in circular motion in the morning and at night.
Whitening soap (Biovalley) wash face with this face wash before applying Whitening cream. Suncare cream (Bakson) apply 30 minutes before going outside and again reapply after 3-4 hrs after washing with Whitening soap.