Separation and divorce are the most painful thing I ever went through. He showed you attention when you left. Didn't he show you any affection when together? Why do you want him to feel desperate for you? Do you just want to be wanted? If the marriage was no good, getting him back will be no different. You have to start accepting its over and start the grieving process. Its hard and lonely but it is what we go through when a marriage ends. Get some healthy support.