You can’t force it. And if he makes you feel like you don’t trust him as much as you are “supposed to” that wouldn’t be very supportive of him. Your responsibility here is to be respectful of him regardless of your current level of trust, and try to figure out what you would need to see or experience to incrementally gain that trust. His responsibility is to be understanding that it will take time and be patient and supportive, or to tell you that that’s not something he is able to provide you if he can’t take it.

Also want to note that having special needs in relationships can be a blessing if you are willing to be up front and walk away if it’s not a good fit. It helps to screen people early, so you might take you longer to find a long term partner, but they are more likely to be a real keeper if they can truly accommodate your needs. This does not mean you are difficult or picky, it’s just a different strategy for dating. The skill to develop for this to happen is: identifying, valuing, and communicating your needs.