Of course you hurt. You are reacting differently than your ex because you are in different situations. This wasn’t a mutual decision. It was your ex’s. He probably thought about it a long time so he had the time to separate emotionally from you and to say goodbye to your relationship. You, on the other hand, were presented with a decision he had already made. You haven’t had the same amount of time to adjust.
Please give yourself a break. People rarely stay in a relationship with someone for 10 years if it means nothing. He did try to let you down easy by telling you that he was leaving to figure himself out, not to explore another relationship. But it does sound like maybe he shared your opinion that your relationship wasn’t the healthiest and has been trying to extricate himself. I wish for your sake that he’d been able to do that without the help of a new person but apparently he couldn’t do it on his own.
Without more information, I can’t venture advice about whether it’s healthy to keep in contact. Most people need at least a bit of a break to regroup before they can explore staying friends with former lovers. Since you are hurting so much, it might be a good idea to give yourself a few months to recover before trying to spend time with him. Focus on yourself for awhile and give yourself time to grieve. I think it will become clear whether the unhealthy relationship can turn into a healthier friendship.
I wish you well.