Firstly, stop squeezing your acne
as it is basically leading to black spots over your face. kindly follow what your dermatologist
has prescribed. Most probably you are not applying the medicines proper amounts and it is irritating your skin. Apply the medicines only on your pimple marks. USe a mild medicated face wash. You can also take some anti acne oral antibiotics
. These will help only in subsidence of acne. You can discuss the option of chemical peels
to lighten your spots. It is always better to treat active acne first and then treating pigmention so that one has desired prolonged effects. You can continue using Spf 20 cream, however using a medicated non comedogenic sunscreen with Spf more than 30 will be more useful.Take care.