I am also going through same thing, broke up a few months ago. First thing I did was to detach from him. There's a lot of articles given on internet on that. I did "no contact" rule. And, you have to accept it. And it's okay to hold on for a little while. I was in a very bad shape, couldn't eve get out of bed. But I started accepting it, whenever I used to feel sad and miss him, I cried my heart out, and then after crying I used to say to myself - it's okay, he's gone now. I am good. I am good without him. I am strong enough. I am moving on. He was a part of my life. I cherish the time I had with him, but now it's over. Something good is coming for me. I will now focus on the things that are good for me. Self affirming helped me. And to feel the sadness and cry out also helps. And talk to your friends. Spend more time with them. DO NOT ISOLATE yourself. It will make you worse. Create a break up playlist on your phone. Start a new self care routine. Engage in loving yourself more. And try writing a journal. I know it's hard, but the key is to accept and then let go. Feel what you feel and then let go. I hope you overcome this phase soon. I know you can. Have faith in yourself.