Strangely enough I experienced a similar situation with my first bf whom I dated when we were 13. Much like your situation it ended suddenly. It crushed me, ached for years (embarrassing to admit out loud), and I constantly beat myself up for it not working, and thought everything would be perfect if we were back together. I had to sit down and honestly review the relationship and where I had been wrong/hurt him (petty things) and when I looked at where I was wrong the anger/obsession started to go away, quickly. It was scary and painful at first but I was so tired of hurting about something 10+ years old. I realized that part of my obsession was what he had come to represent to me (the last stable piece of a life that had become unstable). That's a tall order for a 13 yo boy. I agree with the other users suggestion of therapy, especially group therapy.

As for your current situation, I think it is pretty clear you need to walk away. It isn't fair to either of you and honestly it seems torturous to me for you to be constantly reminded of such a wound. You need to spend time working on you, you are a person independent of Jess. And in that regard, hold off on reaching out to her, if she is meant to be in your life, she'll show up again, but in the mean time I would shift your focus to what you can control: you.

The upside: when I worked on my my life changed so much for the better. I met the most amazing man, it is the most rewarding, caring, devoted relationship of my life. Ironically he looks exactly like the boy I imaged dating growing up (and nothing like my ex ironically). I guess my point is, there is hope, there is a light at the end of the tunnel. Change is scary, letting go is scary, but you'll only drown if you don't drop the rock.