My boyfriend is in prison and I want him to believe me when I say I don't have a wall built up towards him

Hi Betty,
Your boyfriend sounds very insecure.

Have you done anything in the past that would make him not trust you?

Unfortunately if your boyfriend is adamant that he does not trust you, it will be impossible to assure him, given the limitations brought on by his conviction.
You need to decide how much time you're willing to spend trying to convince him to trust you.

You can't convince him of anything. He has to trust you, or he doesn't. If he doesn't you sure don't need him whether he is in jail, or not.

What's really happening is his own insecurities have him tripping, and that's an issue he has to overcome.