depression and such

So my boyfriend and I have been together for a little over a year, we live together and I love him so so much, and I know he loves me too. In the past few days he's been dealing with very severe depression, nothing makes him happy, but he's not really sad either, he's just kind of empty. He's stopped kissing me and when I try to kiss him he asks me not to. I respect his boundaries and I want to help him get better but I don't know what to do because every time he doesn't say I Love You back or he doesn't kiss me back I want to vomit and I start to cry. He says he doesn't want to hurt me anymore but he doesn't understand that what's hurting me is seeing him in so much pain. I just love him so much and I don't know what to do.