Antidepressants are not always the answer. If you want antidepressants you have to be diagnosed with them, especially for younger people as technically we aren't supposed to have them unless we have a serious case of depression. My friend was also prescribed vitamin D tablets which are supposed to help, but there are other methods to deal with depression such as counselling.
I urge you to please not buy antidepressants online because you can never be sure what is in them and the effect they will have on you. At a young age they can be unpredictable and can have side effects in later life as we are still developing. Please look to other ways to deal with your depression before turning to medication, you will find that it will probably work out better for you in the long term.