Actually, I think I've realised that the crux of is that I expect him.to reject me so I'm trying to think of a way of telling him how I feel that doesn't leave me too vulnerable when the inevitable rejection occurs.
I also think you're self-sabotaging here.
You're mind reading rejection, also expecting him to mind read you (and to initiate conversations you haven't initiated either?!), so your plan is to reject him before he can reject you.
When we have a high level of anxiety about something (e.g. Rejection) it is really easy to convince ourselves everything around us proves it and really truly believe it's true even when it's not the case and doesn't appear that way to anyone else. It feels true therefore it must be.
That's how anxiety gets reinforced - the threat feels so real we act as if it is which then creates the situation we were afraid of and reinforces that the anxiety was right.
If you break up with him without attempting to just talk this through with him (rather than internet randomers) on the basis of your anxious belief he was about to reject you then that's the narrative you will carry away from this relationship - that he rejected you.
Except that's not happened! You're just deeply afraid of being hurt.
Talk to him. Say what you've said here. Listen to his response. Stop crediting yourself with mind-reading abilities because you really can't.
Don't sabotage yourself.