What Causes Oily Skin Along With Pigmentation?

I was under treatment of a dermatologist. I have too much oily and pigmented skin. Few months ago I have so much excoriated acne problem. I overcame that with having rouacutine 20mg/10mg and doxicap 100mg. But now I really don t understand what to do with those acne spot and melasma. Doctor said I have excoriated acne, melasma, acanthosis nigrians, Prurigo Nodularies. How can I remove the acne and melasma spots on my face. Do I need any allergy blood test.....though my phisician didn t suggest me any! Can U prescribe me any further medication or procedure for this?? pls help me.........I m 30 years old.