Pretty sure my 6 year relationship is coming to an end

Sara
Friday morning a switch just went off in my fiancés head. He won't talk to me or anything. He just says he's not happy. We are about to buy a house at the end of the month but we are most likely going to back out. He just wants to be left alone and won't tell me if he wants to break up or what. I'm going crazy and idk what to do.