The majority of the time, they don't create doubt. He's been working on rebuilding my trust in him in many ways, but (there's always a "but" isn't there!! ) then I start to think that maybe he's working so hard because he's hiding something. I don't want to be hurt again, so I find myself being suspicious
Then thought control is needed here too, isn't it?
Little by little, that trust is rebuilt. Rather than suspect motives, look at the actions. If they're trustworthy, as you say they are, accept them as trustworthy and build on that. If they're not actually trustworthy, that will come through at some point I think.
What else might you realistically look for, or ask for, that would give you reassurance right now?
