We are very sorry for your pain...
Sadly my wife and I concur with all the above. After reading this thread we both sense that you are unwilling/unable to clearly see what everyone is pointing out. Your need for acceptance and low self esteem will cause you to hold on to hope when there is little reason to hope. Clinging to what everyone seems to have recognized as a relationship that is detrimental to your emotional (and potentially physical) health!
We're newbies here so we don't claim to fully understand all the ins and outs of poly living but we feel certain what you are experiencing isn't what we perceive a loving poly relationship to be!
You really did know what you were getting into when you entered this "relationship" because he was honest, you need to remind yourself how early on you realized that this relationship was going to be tough on you and then ask the question of why you didn't STOP it right then! You appear to be living in misery, when will you be miserable enough to understand that loving someone doesn't guarantee respect or loving treatment in return?