Why have I always been ignored/left out?

First of all, you should probably find new friends. Go mingle, it's not that hard to go up to somebody and start a conversation. Also, if you pray to somebody, you should. Tell yourself every night that you have amazing friends who cherish and care about you. If you have faith, it will come true sooner or later. Sometimes you just have to be patient. Just make sure you separate yourself from the people who bring you down. They are obviously not good for you.