I'm so sorry that you are feeling this way. As Giraffe mentioned, a test result is not indicative of your worth at all. Neither is a lot of other things.
You're still young and you don't need to know what your purpose is yet, if you ever need to at all. I'm still figuring it out at 24 and so are a lot of other people who are even older than me.
Have you talked to someone about how you are feeling?