In my opinion, follow through with your plans. You're working so hard to make progress and you are doing a good job. Opening up about past traumas can be really hard, but I have found that it's really cathartic. Some of my best sessions have been opening up about trauma because afterwards, you don't have to carry the secrets alone anymore and you might feel a sense of relief.

It's okay if he's already read it. You still might want to re-read it to him or maybe you could spend the time talking about it. Eother way, I think it's important to keep opening up to him.