I'm so sorry to hear about your husband, and sorry to hear that you're feeling like this. I relate very much, particularly at the moment. Some days just feel like a struggle, and it's so difficult to get myself to do things during the day even though I know I need to.
I would have a talk to a mental health professional about this, if you have a therapist or psychologist. If you don't, I'd highly suggest you have a look into your options. I began seeing someone a while back, and she was fantastic. I think sometimes it's even helpful to just talk about what you're going through with someone, having them listen to you and validate your experiences.
It may or may not be depression (I'd talk to a psychologist if you'd like a proper diagnosis) but either way, I'll share some strategies that have helped me and people I know when we're feeling down.
Scheduling and making routines tend to work for me, as I like to keep myself busy otherwise I feel low and unhappy. If you're a fan of socialising, you could always (if you feel up to it) try and organise something with a friend for a specific time during the day. This will at least get you up and moving around, and it may even cheer you up. This is only a small thing, but it can have a big impact, especially if you make it a regular occurrence.
Another thing that you could try is engaging in a few hobbies. I myself like drawing, painting, singing, and writing, and I find that they can often be therapeutic if I harness the strength to start one of them. You might not always have the energy for these things, and that's ok. They're just suggestions for times when you may feel up to doing an activity.
Another thing that I know works for a lot of my friends is meditation. There are lots of apps on your phone specifically designed to help out with meditation. I've tried some of them and they're really good for clearing your head and getting you into a happier state.
I hope this helps! Please reply back to us and let us know if there's anything else you'd like to talk about or say. We're always here to chat.
Kind regards, SB