Bipolar/ldr relationship

I've been in a relationship for 8 months and 2 months has been ldr so far. The past week or so my bf has been very distant. And conversation has become weird and texts have become short. I've briefly touched on the things that were bothering me with this and he understood. I asked him if he wants to be with me and he said yea. He is also bipolar. He is on medication. But I'm wondering if he's going through a depressive state right now and I don't know how to ask him. It's been 5 weeks since I've seen him but I'm seeing him tomorrow. I just wish he would stop pushing me away cause he will loose me.