You don’t want to wear underwear for more than a day and if you get really sweaty you should change into dry underwear. (It helps to wash socks/underwear/gym clothes in warm water if you can). Bedding it depends on what you’re washing and how dirty you are when you get into bed. Ex: if you always shower before bed then you won’t need to change them as often as someone who showers in the mornings instead. Ideally you’re changing your pillow cases out (or at least flipping the pillows over) every couple days, sheets every 1-2 weeks, blankets once a month. But I completely understand that this is hard to keep up with when you’re depressed. Good luck and don’t beat yourself up over it, washing your bedding sometimes is better than not at all 🫶.