I understand how you're feeling. It's hard to expect others to see you as something when you think you're the opposite. Self confidence and self esteem are difficult to come by and easy to lose
Try this: In the morning, after you're all ready for the day, stand in the mirror and pick one thing you like about yourself today. (Doesn't have to be physical!) The rest of the day, if you're feeling down or anything, tell yourself that one thing you picked over and over again until its embedded in your brain. Soon you'll have a huge collection of wonderful things (:
Stay strong.