The phrase "nightmare week" refers to a period of time, usually seven days, during which everything goes wrong or becomes very difficult, causing feelings of distress and frustration. Full definition
its the same nightmare week in week out with this old deluded fool. (justarsenal.com)
in one nightmare week where we conceded five goals in each of them (15 in total!). (westhamway.net)
Nights feeds did trail on into the second year for both dc, which I admit got wearing, but overall bf made my life and my mothering so very much easier and more pleasant in a whole host of ways, and was a lovely experience apart from those first few nightmare weeks. (mumsnet.com)