Infertile with a fiancé. Please help.

I have been engaged to my fiancé for three weeks. He is the love of my life and I want to give him everything in the world. Unfortunately, I can't. I just found out yesterday I'm infertile and the chances of me conceiving are 0. I'm heartbroken. I honestly don't know what to do. I know I have to tell him but I'm afraid it will change our relationship. We talk about how we're going to get a house together and have two children, a boy and a girl, that are going to have his eyes but my smile and brown curls......and ugh. I just can't. I stayed at my mother's house last night because I couldn't even stand to look at him. I told my fiancé it was because my mom's going through a divorce and she needed support. Today when he came from work I nearly burst down crying. Right now he's taking a shower and I know I need to tell him before he goes to bed but I don't even know how to start. I haven't even told my mom yet. Glow ladies please help.