The Beck depression inventory is a weekly test (it asks you to evaluate your mood over the past week), so although taking it every five minutes won't tell you much, it is intended to be taken more than once.

If you get a high score, see a doctor. I know how hard it is to tell your parents that you want to get help--boy oh boy, have I been there. But the sooner you get some help and learn how to manage depression, the better off you'll be. And if the doctor determines that you aren't depressed, well, that can only be a good thing.