I don't know the details of your situation, but it sounds like maybe it is time to move on. You can't base your happiness on a single person. The fact it has been several years and you are still obsessing over this individual is troubling. It is normal when you become separated from someone you love to miss that person, to wonder what they are up to and how they are doing. But ultimately, we need to move on. Being in a depressive mood years after being separated is not normal or healthy, it is a huge red flag that something is wrong. It's easier said than done, but perhaps it's time to move on and get past this obsession.