how do you break up and leave the person you love who you have kids with and been with for five years and who treats you horrible and disrespectful :(

I love my partner so flipping much but we have grown apart and he treats me like crap and treats me like a princess once in a blue moon. doesn't touch me kiss me has sex with me and he is just plain and cranky.. hes only become this the last two months and I have tried every thing and he doesn't care, he says he does but doesn't make any effort, I dint want to see him with anyone else though but I can't live like this.. I want to be happy I want someone to want me and love me for me, I'm lonely and he doesn't get it :( how do I leave him and how do I be string and move on