How can I make his walls come down any advice and why some guys think this was?

To start off he’s been hurt by an ex back in high school she never gave him closure after their breakup, she doesn’t trust him. Fast forward to recent like these past months and years he thought he had to play it safe around me he admitted he wanted to date like do coffee dates, do “it” exc But he’s scared and hesitant conflicted and even though he can’t handle much he was mutually attracted to me and I was and still am with him, he was trying for an emotional and physical connection with me but now he says and feels like I don’t care about and his walls are up and I wish I could bring them down.

he also drinks where as I don’t … we made plans to hangout after he was done with rehab ( he’s been in 3 different ones ) but stuff fell through and I know he probably has a lot of baggage, and is back to drinking …. and while I am focusing on myself and trying to not text let alone over text (at least for now) its hard I don’t wanna lose him, I can’t fix him, I wanna love him eventually cause I have a good heart, he loves that I’m also sentimental. It’s been a long time for him and we still follow each other and he watches some stories but I wish his mind was healthier I wish he didn’t have paranoia episodes of feeling “gang stalked/ paranoia”
He sometimes talks about his last girlfriend ( high school ) and I think it’s hurt him so bad and I know he needs time till he knows what love is.

my question is for guys mostly why do some guys have their walls up even when they like a girl how can I get to that connection and make him not feel pressured or hesitant exc or seem like I don’t care for him or as they say she doesn’t like you she only likes being liked.
im sure it’s not me and I don't know if alchol related exc. but I’m always here for him… I don't know what to do, advice?

girls, have you been in a situation like this what did you do?

How can I make his walls come down any advice and why some guys think this was?
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