From what you provided, I don't think that you are losing him. It is quite possible that he is harboring past issues regarding his other loses, which he quite possibly feels he, himself has failed? Therefore, maybe reflects those past failures upon yet another possible one with you?
Fear of failure alone can be a subconscious cause of creating another act of failure, (Sometimes, we create for ourselves what we fear the most).

If he has asked you for space, then you need to respect that. Give him the chance to think through what is troubling him. Do what you can to not invade his time requested.

Have faith in the love you two share. Try to refrain from focusing on doubt and loss, and try to redirect any negative thoughts into positive.
He needs your support. Offer him that support by having faith.
Positive attracts positive.
If he senses that you are doubting the love you two have, it would then seem that that would only support his sense of failure?

I realize that this is a troubling time for you, (and for him as well). However, there is no purpose of having such fears surface if there is no just cause? Perhaps, you are focusing too much on the "what if's" (regarding loss), and not enough on the "will be's" (regarding gain).

Give him a reason to KNOW that you are a safe place TO return to. Be his sense of security, instead of possibly an addition to his already present sense of doubt?

As for your present, while he is away and needing his time alone, focus on you. Do what you can to surround self with positive thoughts.

I hope this helps some.
I wish the best for you and your love.

Shangrala