How do I approach a withdrawn attitude after conflict?

Hey all, so my boyfriend has depression, he’s not medicated and doesn’t go to therapy (even though I’d like him to) and I need some help understanding some things he’s been doing. I am currently on crutches due to a surgery so he has been driving me to and from campus. Last week he fell asleep while I was in class and wouldn’t answer when I needed a ride home so I ended up waiting 45 minutes before calling a roommate to come get me. In the moment I was mad (rightfully so) but when he called me apologizing for stranding me I told him I was mad in the moment, but now I didn’t see a point in chewing him out since he was already apologizing, I told him he could just make it up to me. Ever since then he’s been pretty withdrawn, he refuses to kiss me and when I ask him why he just says “I don’t know, I just can’t”. It’s really starting to bug me, I don’t know if I can put up with this or not. I was wondering if anyone else had gone through anything similar or if anyone has any insight on how to lightly approach this topic. I don’t want him to feel any more mad at himself than he already is.