Pattypoo, there are some people that no matter how much you love them, they don't seem to love themselves. And there's nothing, unfortunately, that you're going to be able to do about it. About the best thing you can do is continue to care, but make sure you love yourself enough not to beat yourself up about the whole situation. There's no amount of love or yelling or anything that will change things.
They're not doing it because they don't love you. They may only 'get the point' when it's almost too late, which is a shame.
It's unfortunate, but true.