Long distance

What do you do when your long distance boyfriend has trust issues because you have a child with another man? I haven’t been in a relationship with my son’s father for over 3 years now and i’ve been single up until recently when this guy who i’ve known for a few years who lives in another state asked me out. I like this guy more than i’ve liked anyone in a very long time and I would love for it work out but he has trust issues and is worried my ex will change and I’ll want to take him back. I am certain that i would never give him another chance after everything he put me through. I have tried to convince my boyfriend that I would never get back with my ex but he still thinks it’s a possibility and i feel that it’s holding him back from being completely happy in our relationship and i don’t know what to do about it. I don’t want to end the relationship but i don’t know what to do about the situation. I know it’s even more difficult being long distance but I am not sure what to do or say to him anymore. :/