How to get him to open up again

Recently I've started liking one of my guy friends and he starting falling for me too but someone said shit about me so he's one to believe shit we had an argument about it because why would you believe someone you barely know who's talking bullshit about your friend anyways. But anyways we used to see each other everyday and text all the time and after that he put up a wall towards me and I hate it. I see how hurt and lonely he is from his previous gf and he told me I was the only person he let into his life again but I feel he got scared what do I do to make him feel safe again because I really wouldn't hurt him and I've told him what's up on how I'm feeling and he doesn't show much emotion towards me because I sense he's holding back. How do I get him to open up again I want my best friend back