What you’re going through sounds similar to what I’m currently trying to heal within myself. I think a good place to start is attachment theory as you’ve touched on. I’ve had similar attachment issues and am working on uncovering the core negative belief rooted in my initial experience of abandonment. I've explored many negative cognitions my original attachment rupture could have triggered, such as "I am not safe," "I am not loved," and "I am bad," but none truly resonate with me as to why it’s so difficult to let a certain attachment go. This led me to ask myself two questions: "What would life feel like without this person?" and "What void does this person fill in my life?" I could easily see the core negative cognition then. For me it’s not so much about “I’m not loved” but “I do not have access to love,” there’s a tiny but distinct difference. There are few others attached to this core cognition as well, most pertaining to lack of joy, lack of fun, just plain lack in general of all things that feel good. 

Unpacking issues like these are complex, and there’s not really a quick fix to healing them. The original attachment rupture often occurs early in life, in our formative years, and subsequent traumas add new dimensions of negative beliefs. You can heal these beliefs by replacing them with positive ones that feel true. That your rational brain can accept as true. 

If this resonates, I strongly recommend exploring EMDR therapy.

Well, I saw him yesterday and the connection is gone. He was very flat with regards to me (said hi, gave me a hug, asked how i was doing, moved on to talk to other people). Absence made his heart grow a lot less fonder, just not mine. I feel like an idiot, of course. Last year at this event he ran up to talk to me, this year...meh. I'm an idiot. It was probably never mutual.

Back to being hopeless and alone in space. I thought Uranus going through my seventh house would bring me opportunities for once, but...nope. And Uranus in seventh runs out this year, tool.