When I read through your posts, I realized that your heart is broken. Thle loss of your girlfriend made you feel your feelings anew, but people who respond as you have to such a loss, are generally people who were abandoned by someone essential as a child.
Your girlfriend was a proxy for that person or persons in this case -- probably a parent. Your love for her, is like your love for that parent -- who abandoned you in some way. The reason you are having trouble moving on is that when you believe someone is as essential as a parent, and you lose them, you lose yourself. . . again.
This happened to me not so very long ago. What helped me was a multi-pronged approach involving
1) Forgiveness - Gary Renard's Disappearance of the Universe and ACIM helped me and still help me every day. You need to work on forgiving this person, and releasing her to her good. It will help you also to forgive yourself. I would suggest that you are blaming yourself and feeling unloveable because you came to believe some things yourself in your youth that are not true. It isn't true that you are unloveable and abandonable, but it probably feels true to you because of your past.
2) The acknowledgement that the love is real. Your love for this person is real love. Now that she has rejected you, you need to move on. I couldn't stop loving, so I let myself show my love by giving that person up, as requested. Entirely -- gave him up. I suggest humbly that you need to give her up entirely, as I did. Because she asked you to, and because you love her. When you love someone you give to them what they ask, and wish for the best for them. In this case it is critical that you give her up entirely. Forever. And find yourself.
3) The concept that this world is a dream, and not reality. (Gary Renard again, and ACIM). I found that in my mind, if this world were real, and my ego was real, it was too very painful. As a person, buffeted by rejection, betrayal, abandonment, death, loss, all of those other experiences which humans have when times are not so good -- it was too much for me. But as a dream world, with something real, a nondual reality for all of us, behind it, I can experience that the love is real, and only the love.
4) Drugs and other support helped. When I couldn't sleep, I took valium -- at night -- over a two month period. I went on antidepressants. I started seeing a counselor, someone I really trusted.
5) PTSD support. I was diagnosed with PTSD -- and PTSD doesn't respond to 'thinking' cures, because it is about an imbalance in the limbic portion of the brain, which DOES NOT hear your words or respond to them. Approaches which helped with the PTSD included learning I had it, and treating it with the tenderness and care needed. EMDR helped -- and you can do it on yourself (there is a do it yourself EMDR book you can buy from Amazon and I recommend it). Drugs and cognitive therapy don't seem to reach the PTSD, except to help with the symptoms -- you need to address the underlying PTSD itself. I have a friend who has been through trauma, who didn't have the $$ for therapy -- the EMDR worked wonders for her -- changed her life. It has helped me as well. . . .
No one has all the answers -- and I could be wildly off track he here -- if so please forgive me. It just seemed that as I read your posts, I might be able to help.
Bottom line, it is not PC to speak of broken hearts these days -- but your's sounds like it is in pain. IMHO, acting as if it is not in pain may not help one bit, it may even make it worse.
I hope this helps -- it is personal and hard to posts these things for me, but if it helps, that would be good.
Blessings from Belle