I have a feeling that by "factual and mature" you mean to interject distance.
it's ok to feel however you feel. He will take it however he takes it, regardless of the distance you try to create with what you write. Yes, the rejection fear can be huge, and no one can promise he will react well, but most competent therapists know how to handle attachment.
Being attached doesn't make you immature or weak or pathetic. It's one of those things that comes with therapy When you poke at the hurt little inner kid.
Admitting strong emotions can be scary, but it has a lot of potential too.
I hope you can find a way to talk to t about it.