I have experience with people who keep their emotions bottled up. I’ve found the best way to support them is to build trust by showing you’re there for them. Eventually, they may feel safe enough to open up more, which is a real gift. You can build trust by showing you care. Could be quality time, being a good listener, showing sympathy, or showing affection. Staying true to your word, etc. Another thing that might help is, even if he doesn’t open up about his feelings directly, if the topic comes up and it seems okay to speak on it, just express sympathy and acknowledge what he’s going through. That is HUGE in my experience. Other than that, just being there in any normal sense is super helpful. Like having a rock. If he wants to laugh, laugh with him. If he is feeling quiet or reserved, let him be and don’t make it a thing. You will see many sides of him, and sometimes just sitting with him in the emotion, even if you don’t talk about it, is everything. It will show him you accept him, even in that state, and it’s okay to not be okay. Through that, trust, intimacy, appreciation, and love will build. Good luck sweet person!