Partner became emotionally distant after rehab – how to handle this?

I’ve been in an online situationship for several months. We met through a game. Early on, he told me he struggles with burnout and depression. He recently spent a few weeks in rehabilitation. During rehab, communication was good, we talked every day. On the last day, after a conversation with his doctor, he told me he felt really bad and had no energy for anything, but that he would explain later. That was 4 days ago. Since then, we’ve only exchanged a few short messages. He ignores emotional messages, but occasionally reaches out to help me with the game. When he does, he’s emotionally flat, no warmth, no affection, no real conversation. He also doesn’t want to talk about what happened in that doctor’s appointment. One night, he sent me an emotional song in the middle of the night, without any explanation or text, and then went quiet again. I’m struggling with this sudden wall he’s put up. I feel sad, confused, scared, and also a bit angry, mostly because I don’t know how to act or what this means for us. Has anyone experienced something similar with a partner dealing with depression or after rehab? How do you cope with the emotional distance without pushing them away and without losing yourself?