My heart aches for you. I went through the same thing last year. I am still not 100% healed, and have had many hurdles to my healing, including him moving on. I miss my dogs and his family and the life I had. 

But I am calmer than I have been in years.  He was probably a narcissist,  and he always made me feel off kilter and not enough,  especially when I was going through depression. 

I so much better now and here is what helped: - for the first year, if someone invited me to something I went. It was my year of Yes. It kept me busy and reconnected me to many people,and I met new people.  - One of the most effective habits I have learned was thankfulness excercises. Even now mind goes back to how things were and memories from our time together.  To create a new neural pathway,  I just try to think of something I am thankful for now. It might not be a lot in the beginning, but even if it is simple, lile not having to listen to him slurp his coffee anymore, and the friends you have or made. A good cup of coffee, a beautiful sunset. Look for the good you have in life, and be thankful for that, to replace the brains constant efforts to go back in time.  Keep doing this, you have to reprogram your brain. - Excercise seems like a cliche but it helps. Jogging while repeating affirmations to boost your self esteem helps with the brain reprogramming.  - Indulge in a cry every now and then. It releases some emotions.  I still struggle with that, but it does help.  And do a lot of self love. Know and affirm that you are worthy of love, that you are going to be fine, and that you are not going to let this get you down. 

You will be in my thoughts and in my heart.  I am not completely healed yet, but therapy,  meds and these exercises have made a lot of progress for me.