Hello and welcome to the forum. It is hard to learn of the death of someone you love no matter that you separated a while ago. Please accept my condolences for your loss.
Grief is a funny thing and seems to go away then come back when least expected. Although you are finding it harder each day to manage your sadness there will come a day when you notice you are not hurting as much. At the moment this means little to you because of the really horrible pain. Just keep this in mind.
Do you have someone to talk to? I don't mean a psychologist etc but a friend or family member. Are there any children from the marriage? Perhaps you can talk to them if they are old enough. If I have put my foot in it please excuse me. I am looking at the things that have helped me when someone has passed away, my parents and sister. Also in many ways, my separation from my husband.
It helps to talk about your husband and remember the good times you enjoyed. So many people try to push down these memories thinking they will make everything worse. And yes it can be a little hurtful sometimes. On the whole though remembering, laughing at the silly things that happened, looking at the things you did together can be a great help. It will not bring him back but but is a good way to start letting go of your pain. A friend of mine said she was told when her son was killed in an accident, "You will never forget, but the times between remembering will get longer". I think this was very beautiful, reassuring and for me very true.
Again for me, feeling constantly tired and only wanting to sleep was a way of coping. Waking every morning and remembering is so devastating. Apart from talking about your loss can you get some exercise? Apart from the obvious health benefits exercise, exercise releases endorphins into your body which help to make you feel better. Perhaps a walk in the morning instead of staying in bed. I know at times this will seem like climbing Mt Everest but try to do something every day. Join a Tai Chi group in the park, anything that gets you moving.
How do any of these suggestions feel? Probably a bit useless but I assure you they work. It is part of the reason for your continued tiredness and anxiety. Most dogs like to go for a walk but the black dog (anxiety) wants an easy life and will try anything to keep you miserable.
It will get better. Please continue to write in.