Hi.
I'm really sorry to hear that you're feeling so depressed.
Though it's not exactly clear what causes depression, one of the most commonly held theories is that people who suffer from depression have imbalances or deficiencies in the amount of neurotransmitters--biological substances that allow brain cells to communicate with one another. Seen through a biological lens, depression can be compared to other manageable conditions, like diabetes in which the body either doesn't produce insulin or is unable to absorb and use the insulin that is present.
While most people would probably think a diabetic is foolish for not taking medication to help manage their condition, many often think it's shameful to need help with something that appears to be related to emotions. Though there can be contributing factors that come into play such as a person's genetics (a person whose has a parent that has suffered from depression is more likely to become depressed) or environmental stresses (a breakup, illness or a negative self-image), thinking of depression as primarily a medical condition might help you to feel better about getting the help you need.
There are also other things besides depression medication that might help lift your mood, like exercise, but I would recommend that you also talk to your parents about finding a medical doctor who can do a thorough diagnosis and create an appropriate treatment plan. Psychiatrists usually find that their treatment works best when their clients are in talk therapy as well. Your medical doctor or school psychologist can probably help you and your parents with referrals.
gURL.com also has some helpful features on depression. You can find out how other gURLs feel about mood medication and get the facts on depression.
All the best,