This is an informal expression meaning to be thoroughly confused. It has another meaning as well. When things in and around the house are at sixes and sevens, it means everything is totally disorganised; in general, things are in a mess.
*When the management changed, we were at sixes and sevens for a week. *We moved in last week. Everything is at sixes and sevens in the apartment.
There are several different explanations as to the origin of the expression. According to one theory, in the 14th century two companies, “Merchant Taylors” and “Skinners” were set up within a few days of each other. Every year all companies in the city of London took part in a procession; the order in which they appeared was determined by the age of the company. The two companies were listed sixth and seventh, but since they were established at about the same time, the organisation in charge of the parade could not figure out which company was to go sixth and which was to go seventh. There was a lot of confusion. The matter was placed before the Mayor, and he decided that the two companies would alternate. The company that went sixth this year would go seventh the following year. This is one theory. Some others believe that the expression comes from the world of gambling — playing dice.