When I lived on my own I often felt like that on a Friday and sat night, if no plans. I used to stop off at the supermarket or m&s food on the way back from work, get a nice bottle of wine and a nice pizza/ ready meal, sometimes a nice pudding too, and have a lovely night watching a film or just tv. Always cheered me up.
Hope you feel a bit better soon. Just getting out to the supermarket will help.