to get most antidpresnts you need a perscription from a dr who will perscribe one safe for your age group of it is neccery for you to take them and will also closly monoter your conditiopn to agust the dose as neccery. in the uk at least it is not posible to bie antideperts over the counter, only herbal/alternitve recipys which act in a simmaler way althogh these come with strong warnings and most phamasits will stronly advise a visit to the dr anyway. no antidesnts as far as i know are avalable to anyone without perscription from a suterbly qualified medical practioner.
if you are conserned about your mental heath you should see your dr and get a proper assesmet, this is the best way to get peace of mind about what is going on