I need help

I have been dating my boyfriend for almost five months. We have had a really solid relationship and he always told me how much he liked me and would stick with me through my issues that bothered him. The past few days he has seemed distant and then last night he asked me if i felt like our relationship was falling apart. i said no and i asked him if he thought so and he said i dont know somewhat. i then asked him what made him think that and he told me that hasnt felt motivated to talk to me for a few days. i asked if he still cared about me and he just said i dont know. i was trying to talk to him about it and he said that he didnt have the energy to deal with this right now. after that i told him that i would just give him his space for a few days. this has made me feel awful and he has never been like this before. he has depression and sometimes doesnt feel motivation for things but he did not tell me that he was feeling depressed then. i really dont know if someone can all of a sudden stop caring about someone and i am really hurt and confused. i just want to know what to do.