Thanks for bringing your question to JustAnswer.
I would strongly recommend that you not see him until he gets better. Clearly, this is not a man who is ready for a live-in relationship. It is highly unusual for someone who has been in a relationship for 10 years to react with severe depression when asked to go to the next level.
If he is this conflicted and desperate not to discuss moving in, then the next question is if your life goals are compatible. If your eventual goal is marriage (or at least living together in a committed relationship), I would strongly recommend couples counseling once he is out of this deep depression.
If he won't agree to that, go see a therapist by yourself. You need someone to help you figure out if this man has the same plan for his life as you do. You have given ten years to this relationship, and you need to figure out how you will feel if it never goes any further than it is now--living separately.
Moving in while he is in such conflict would be a very, very bad idea. Drop the conversation completely until he's out of the depression, and then try to get him into couples counseling. He's already on medications, but he may want to have them re-evaluated--they may need to be adjusted. He also may need individual counseling as well to help him recover from his early trauma.
Thanks for your advices. 1. You recommended me not see him until he gets better, but I am worried about him. He has no family and few friends. I wonder if his depression will get worse and he will be at risk if I stop seeing him. What would you think? 2. If I break up with him whil he is in depression, should I stop seeing him completely or maintaining freindship until he recovers is ok?
It sounds as if you think his talk of suicide may be an actual risk, so that changes the timeline of the advice I gave earlier.
If you're worried about his safety, then continue to see him as usual until he's through this. For now, keep things looking the same --but stop the conversations about moving in. You've been together on and off for ten years---a few more months may help him get through this crisis.
Do you think he would be responsive if you asked him to go see his MD to have his medication adjusted? It clearly isn't working (or maybe he stopped taking it without telling you.) Stopping antidepressants too fast can cause the person to have a discontinuation syndrome
and they can feel worse than they did before they took the antidepressants.
The first priority is his safety. If you feel he may be suicidal, then do everything in your power to get him help. Once this crisis has passed, and he's gone back to his usual self, then will be the time to have a talk with him and decide if you're going to be back together in the future. However, don't take all the responsibility for keeping him alive. He needs professional help. Here's the site for the National Suicide Prevention Hotline