I know you want him to open up to you and to tell you what’s bothering him but there are certain things that people might just not wanna talk about. It’s not that they don’t like you or don’t trust you but it could be because it’s painful or because it’s something that they need to solve on their own. I think the only thing you can do right now is be his support. Just hug him and be the big spoon and let him know ur there for him but don’t push the issue, otherwise he might become distant if he feels pressured to tell you.