Re: what should i do..
Perhaps go to another dermatologist? Tell them your experience with the medicine that the first dermatologist prescribed you and ask for a second opinion. There are honestly so many remedies to acne .... and not the same thing is going to suit everyone. My sister has really bad acne so I know this first hand. She has tried so many medicines and creams and even herbal remedies before she figured out what worked best for her skin. (daily diet, face wash, face toner, acne medicine, makeup, etc). Some of the stuff she tried had HORRIBLE effects on her face and it was worse than before. But that did not mean she stopped looking for a solution.
When something does not work out in life (no matter how big or small) - that does not mean one should give up. That constant desire to find a solution, improve/enhance an aspect of one's life is such a positive driving force to living without getting too down about the daily struggles we face.
I agree with others that you should see a doctor- as this could be a hormonal problem. But I also advise against taking anti-depressants (even if your doctor is quick to prescribe them). Perhaps go see a therapist??? I had a friend who had hit a low in life and no matter how much support her friends and family gave her ...she could not get herself out of that state. She went to a therapist and it really did help her. The therapist was a constant reinforced for her to change up her life. To do things differently. View things differently. It was a very positive experience for her. It might be for you as well.
And Saddzz is completely right. Enjoy life girl... because it is truly too short. Spend time doing things that truly make you happy....no matter what it is. Make sure you take time out of your life to do them.
Why don't you plan a mini-vacation trip with a best friend???? Those are so great when one starts getting sick of the same routine of their life or are low in general. Quality girl time in another city/place is great. Take the time to plan the details of this little trip... where you will stay...where you will eat.... sightseeing.. etc. It will make you think of things other than the norm and you will come back so refreshed inshAllah. :)