Amanda,

I think that many young women have been where you are. I suffered greatly with sadness and self esteem issues when I got out of high school. I think that for me, what has helped me to overcome my feelings of insufficiency and worthlessness, has just been to try to love everyone around me and use my talents to make life better for others.
It is possible that you may need counseling or even medication to help balance things out or to be able to sort through the pain and the fears, and there is NO SHAME in needing help. I have been to counseling, and also take Paxil to help control my anxiety issues (though currently I am pregnant, so I am off of the meds temporarily!).
Buddhism has taught me to keep in mind that all things are temporary, both good and bad.
It will not always be this way! There will always be ups and downs, but overall, life is a beautiful gift. You will do great things in your life, don’t let negativity keep you down! I’m rooting for you! 🙂