I think, for now, maybe write some things down. Don't get hung up on trying to make it sound excatly like you feel because as you said, it is too hard to express that eloquently. But maybe some bullet points and some a little bit of explaining in detail. I think if you could just have one or two important things expressed to your cpn that would at least be a start.
The thing is that this communication thing doesn't just start working on its own accord. You have to practise it. And it's okay not to be fluent at it in the beginning. It's okay to not be able to find the exact words to express everything inside but i feel it would be good if you could get across some points which are important to you.
I don't know how you feel about this but would you be able to steer the conversation tomorrow in the direction you feel it should go???