Greetings! thanks for the query.
Acne problem is very common in your age group. Correct medications used in the initial stages will control acne and prevent scarring and black spots. There are many treatment options available including creams (combination of retinoic acid and antibiotics like Clindamycin/ Benzoyl peroxide) and oral medications ( in moderate to severe acne). You still have active acne problem and I would suggest you to see a Dermatologist for customised treatment plan. I can assure you acne problem can be controlled if you adhere to the treatment plan.
Acne is not caused by eating junk food. Please read my blog which explains in detail why people get acne
http://dermcureclinic.blogspot.in/2016/11/why-do-i-get-acne.html
Once acne is well controlled treatment for scarring and black spot can be initiated.
Next Steps
Please visit a Dermatologist for evaluation and treatment of your condition.
Health Tips
Please avoid delay in seeking Expert opinion as it will lead to delay in the initiation of appropriate treatment leading to (avoidable) complications.