This is sort of the question I want answered too :( My guy has trust issues and I just want to prove to him, that I'm not going to hurt him, and that I love him too much to do so, he just has problems knowing the truth from lies, but here's the things I do to prove to him that I really love him, I don't know if its working for me, but it may work better for you...
Find want interests him the most in life, like a hobby or something he likes to do, and just be really supportive about it, my boyfriend loves basketball and he recently just tore his acl and other things I'm not sure of the names (lol) but right now he's pretty depressed about it since he can't play until 6months from now, and he's afraid that he won't be as good as he was before the injury, but when he's down about it and wants to talk I always reassure him to be opptimistc about things and not too give up,
When he's with you , hold him. I know this might sound like the GUYS job but when I do it, my boyfriend says he likes it a lot because its like secure, I don't know how he described it but I guess it makes him feel special, kind of like how us girls feel when they hold us,
Be jealous. just a little, this will let him know that you want him to be for you and for you only, but don't be too jealous, I know this will be hard cause its especially hard for me, my boyfriend has a lot of female friends and I can't help to think that they like him, or he likes them., because its normal for humans to be attracted to other people, but don't go overboard with the jealousy cause it will lead to fights and arguements :( speaking from expierence, sometimes I get so emotional that it gets out of control, and it "annoys" him
But when the guys say don't be too obsessed we should listen, because then they do get a little "big headed" and think you're there to stay for ever, when its really we're getting tired of how they act, I'm having a hard time to not showing obsessivness (if that's a word lol) because its hard holding feelings back, but we just have to try really hard.
hope this helps. :)