Words of wisdom from the radio oldies: Darlin if you want me to be
Closer to you
Get closer to me
Darlin if you want me to see
See only you
then see only me

(and so on and so on.) Try to love the one you're with if you can. Try to focus on how much love and understanding you're giving more than on how much you're getting, more on what needs of hers you can meet rather than on what needs of yours she has or hasn't met. This may or may not work but it sure can't hurt, and it might do wonders.