Ok, dealing with the weight is a long haul process - have you ever successfully lost weight before and if so can you do that again?
Get some exercise, even if it's only going for a daily walk (ideally somewhere green) Good for body and soul.
Look at adding yoga or Pilates (lots of online resources, you don't need to go out to do this) and even if daunting, consider C25K
What's your hair like?
Even if you're not finding the energy to do a manicure and maintain varnish, at least use handcream daily and shape your nails.
Get a nice perfume - just as a treat
You can still dress for comfort, but it doesn't have to be drab. Do you have any budget for new stuff? I'd limited, then look for things like scarves in supermarkets or charity shops. Having something new, with colour (especially near your face) can give you more of a lift than you'd expect.
Get enough sleep
And there is a mindfulness practice that might help you, which is to write down every evening a list of 10 good things about that day. Doesn't matter if you struggle to spot them, or how small or tangential they are. It means that you won't be spending all your time and thoughts on the negative. Sounds a bit forced and cheesy? Doesn't matter, it's a growing habit.