I feel for you, travelsafar. Try not to be too hard on yourself. Grief takes many forms, there is no correct way do it and there is no time span for its duration. Also, don’t be afraid to open up to others about your feelings, they are there for you. I’m sure if the situation were reversed, and someone opened up to you about how difficult they were finding some things, you would help willingly.
I understand your hesitation regarding the house move. I imagine it’s the home you shared for so long with you DH, so therefore is full of memories and pulls. However, our memories remain with us, in our heart, wherever we go; and hard though it will be to move, you have to consider your future well being. At the moment you can probably cope with the house you’re in, but soon this may be more difficult?
The good thing about the flat is that it is still close to the things important to you - family, friends, amenities; so it won’t be the wrench it could be.
Don’t be rushed into a decision, though, but listen to that little voice in your head, and follow that. Once you’ve seen the flat, you’ll be in a better position to reach a decision about it. Is there someone you could discuss it with?
I wish you well.