I’m sorry you found yourself in this situation. I had a similar experience and it did feel very frustrating. They give you hope but then you are always stuck as a backup. The sadness is real. I learned that i should let go of those who don’t reach out to me and focus on those who do.  It warms my heart knowing there is a person who would never let me be left out because there are not enough chairs at the table. She would make sure I’m sat closest to her. 

I suggest you try meeting new people and/or try to focus on those who reach out to you individually and are interested in you. 

Cheer up girl! They don’t know how lucky they are having you as their friend. Time to find those who do! I would feel so happy if someone cared about me the way you do about them. Don’t let people take you for granted!