Exactly and I think in the end it hurts you even more knowing you cared so much and did so much when they did not. Then the end of the relationship. Its part of the heartbreak.

This is how i feel too. I hate feeling like i have done to much for someone that has not done enough for me.

To answer your question about feeling like you cared too much.
Yes, after every serious relationship (which has been three) I feel like I have cared too much and put too much effort in when it seems like they have not. Even in the less serious ones I feel that.