I can see why you are devastated. The first thing I would be asking him is why he needs you to leave while he works on himself. Why can't you be with him while he heals the past? Why does he think that your presence would prevent his healing? Why does he need to suffer alone (male pride)? Is he using his past wounds as an excuse to end the relationship and let you down easily?
I wouldn't let him off easily. I would insist on his telling you what it is about you and/or the relationship that he wants to run from. You might say, 'I think that you are trying to protect me from the truth. . . I don't buy that this is all about you and your past. If I weren't part of the reason for your discontent, you'd be having me stay close to you and help you through this crisis.'
You might also try getting tough with him by saying that you refuse to leave while he's in crisis. No decisions should be made when someone is upset and that you are not going anywhere until the storm passes. Tell him also that he needs to be in individual therapy in order to work out whatever is coming up for him. Hiding alone is his cave will never heal him, nor will time alone do the trick.
I hope that you can succeed in getting him to tell you the entire truth about his feelings. If you need help getting him to talk to you, then go together to a couples therapist. Good luck on getting him to open up.