It sounds like he's put up a boundary and is not interested in a relationship with you any longer. He may have his own reasoning. Perhaps it really is for his own mental health if the relationship was causing stress because it was not healthy for him. As painful as it is for you to accept that, it may be that you have to respect that boundary and allow him to move on without you. My guess is that trying to continue to contact him under the circumstances would not be helpful to either of you.