I do believe in true love, I do believe in love at first site - however I also know that it is possible to love someone so completely, and have nothing returned. Especially when its someone you have to see and speak to every day.
I have been in abusive relationships or relationships where I was respected as a person for my own opinions or I felt that I was only liked for the physical. Even from strangers or aquaintances I get hit on for the physical and it is frustrating. I didn't grow up with love and acceptance from either parent and I was also neglected at points and it made me realize that I have been loving guys who don't love me for the right reasons to fill that void my parents left me. I realized at least for myself that I don't know what true love is because like you said 'love someone so completely, and have nothing returned.' How is it possible to love someone that doesn't love us back. I have been showing love or caring I believe (besides the fact that that is the type of person I am-caring/doing the right thing), however I do it to those that don't give back because that is all I know (same as my relationship with my parents) and I am trying to reach out for them to understand me/for them to give back. I have also learned that generally those people that don't give back/don't know how to love were also hurt or neglected as children. It is similar with depression-there are people that turn to food to deal with their depression and there are people that starve themselves. I hope I helped you and others to think about all of this. Hang in there. Life can be good, but it doesn't have to be based on someone accepting us or not. We have to feel good that we are good people and if one person doesn't like us (truly like/love us) there is someone out there that does/will, but in the meantime we like ourselves.