Because you can't adapt, when a person is used to something and suddenly loses it, he can't adapt. In fact, think about what you were like before him, and now you just go back to that time. This is a big blow. I know how you feel. I used to be a free diet pill.
Have a good rest. When you are alone, summarize your past. I know you still love him and care about him. Since you can't be a lover anymore, let him be happy! Emotion is a matter of two people, of course, it can't be forced, it is mutual, and it will get better after a while. Maybe you will hate him at first. Think about it carefully, after a long time, you will hope that he can be happy, and love doesn't have to be together!
Have a good talk with your intimate friends and tell them all your unhappiness, so that you will feel more comfortable. Don't drown your sorrows with anything. Although you may not want to eat, or you still can't sleep, you must force yourself to eat and have a good sleep! Because you still have a bright future!
Try not to let others see how unhappy you are, just know in your heart. If you still need to adjust yourself, think about his bad points and hate him. In fact, if your's feelings are still together, you can go to see him after a while, maybe tomorrow will be fine. Remember, it's really impossible, so give up. Time will change everything.