Do I need to cancel our wedding this May?

I 'm not sure whose fault was this but here let me explain real quick: My Boyfriend and I live together for 6 mos. now. In October his sister stayed with us. We talked about it and agreed that he is gonna shoulder the 'extra' expenses when she comes in.And now he's telling me that I am nagging him about not being able to save for our wedding and he is telling me that Im treating him like trash. I dont even talk about being fair in the share(bills and rent and food). Sometimes I shoulder everyhting w/out asking for anything in return. i just think i didnt have to spend for his sister bec. we are not married yet and she's 27, too old for to help her out. i mean...she can't even find a decent job...so now he's threathening me that i'm gonna spend Christmas alone coz they'll be out of the house. He said we should only be together after the wedding but i dont wanna marry him no more.prob is we have invited people to come to our wedding...HELP.