Perspective filters everything. There probably aren't a lot of things in your life that you are excited about or take pride in- which is understandable given the situation but it is also partly due to a defeatist attitude and withdrawing. If you had just a few small things to look forward to or a few new things to explore and put your focus and attention on, you would notice that your grip on the past and others will loosen and you will start to re-build yourself. Right now it sounds like you are neglecting your body/soul/mind and dwelling on the past and people who are no longer part of your intimate life. Allow yourself to be selfish in a healthy way. Take care of you.
I was depressed for a while after a relationship that went south and I finally got to a point where I realized that I just felt horrible every second of the day. And I asked myself why and I realized that it was because I was literally abandoning my own body and mind. I can never change another person or the past, but I do have the power to change what is in my control- ME. In that dark moment I decided that if I am going to feel miserable and awful, I might as well feel miserable and awful while doing things that will help myself. I also told myself that I accepted that I had grown weak as a person but that I would start re-gaining control of my life where I could, and so I started to take control over my eating habits.
I overhauled my diet and in 3 weeks I lost 10 pounds. And by the 4th week, I started to feel stronger and more in control of my body and mind, and I started to run and lift weights. Eventually I had re-gained pride and control over my body and that did a huge number on the confidence of my mind. I truly believe that part of my depression stemmed from my body/mind being neglected and poorly taken care of. I don't know what your diet and exercise is like, but if it is poor, you can do a lot of good for yourself and your pride and confidence by letting your emotional rock bottom grant you the freedom to slowly take back control of you.
I hope it works out and as others have said, time does help. Build yourself back up so that when you meet the next love of your life you are in a healthy place and can take advantage of it.