Having a hard time after boyfriend ended 4 year relationship

My boyfriend broke up with me about a month ago and I just can’t get over it and move on. I’m still feeling physical pain and heartbreak. Can’t eat and can’t sleep. I know you’re supposed to do the “No contact” thing but I can’t. I still text him and sometimes he will text me back and occasionally he will text me out of the blue. I didn’t want this break up and can’t imagine life without him but I also don’t understand WHY I want to be with him so badly when he obviously doesn’t want to be with me. Why can’t I accept it? The pain and hurting is really starting to take a toll on me. I just can’t understand how he can just throw me/us away like this.