I cannot tell you when the pain will end, but I assure it will. My ex-wife left me after being together for 23 years, 18 of them married. That was about five years ago, I was 45, and at the time, I felt exactly like you feel now. I remember walking alone into my new house and not knowing what to do with myself. I ended up literally walking around the house in a daze for hours. I did not have the will to make any decision, not even to sit down. Not even to turn on the lights as it got dark. I just kept walking in circles, by myself, in the dark. For months, I felt like a shell of my former self.
But things got better. Slowly, for sure, but they did get better. The pain slowly diminished. The spark I had slowly returned. Eventually, I even started laughing again. But it took time. It will take months or years, not weeks. I know that feels like it is forever, but I promise you it is not. You are in the hardest part of this right now. The shock is wearing off and the focus is on what you feel you are losing. It is terrifying (at least it was for me). All I can offer is that for me, and many people I’ve met in our same situation, things get better. Better than they are now, and even better than they were before the divorce.
The best advice I got, and that I will pass along, is to focus on taking care of yourself. Be kind and forgiving to yourself. Have faith that with time, you will feel happy again. The pain will stop. Please just stay strong, keep getting help, and be patient until it does.