I know this won’t be the end of it. I’ll be under pressure to get back together etc etc.
I think it's best to say something that cannot be argued with and just repeat as necessary.
How you feel, what you want. NOT what he has done or what he is like. Because he can argue with those things and try to get you to see things differently.
I'm sorry but I don't love you any more
But I can change I know I've been difficult
I don't love you anymore and I can't change that
You can, I'll be better, we can change things. We can get the love back.
No. I don't want to. I don't love you now and that isn't going to change
After all I've done for you, and this is what I get. You're crazy you don't know your own mind
I know I don't love you. And this is over
I'm sorry! I need you, I think I may have a serious illness, you're everything to me.
I do not love you, and I do not want you here, and I do not want a life with you. And I won't be marrying you
But but but but....
I don't want to be with you, I don't love you, I won't marry you, I don't want you living in my house, I need you to go
But where am I supposed to go? What will I do? You can't be serious...after all this time you're just going to chuck me out, you'll never find anyone better.
I. Do. Not. Love. You. Please. Go.
But the wedding! I love you! I'll do anything!
I. Don't. Want. You. You need to go. It's over.
Don't be drawn into discussion. Just decide what you want to say and keep saying it.
Very best of luck! 