Hello Pimples occur due to blockage of oil from oil glands in the skin and it occurs under hormonal influence. 13 was the age when many changes started happening in your body including hormonal. Taking treatment from specialist as soon you start getting pimples is best idea. No home remedies will help perfectly. Certain factors which may aggravate pimples are stress, oil based occlusive cosmetics and food items like milk and other dairy products. Pimples usually leave behind spots and chances of dark spots increase if you fiddle with them. Please visit a dermatologist asap for proper advise and treatment. Keep patience to see results.