I have been feeling similar to this lately, a loss of knowing who I am. I think it comes partly from looking too deeply at things and into yourself. You will be better in touch with life and things and people around you if you focus outside yourself. Focusing inward is going to cause you more confusion. This is what I have learned from experience over the years. I tend to also analyze and ruminate, and this is the road to being unhealthy mentally. You have to pull your focus away from yourself, don't worry about who you are right now. Just look around you, know that you are part of this world and have a place in it. You ARE in reality, you are part of your own life. You are living your own life and are an integrated being. Trust in that, and pull your focus outward. You also need to see a therapist or someone who can train you in coping skills and methods to practice doing this because it is a slow process, and not as easy as it sounds. Your mind is always trying to pull you inward and you have to pull yourself outward. It might feel all wrong, but it's the right thing.
Allow the universe to just be, and know that you don't have to ask yourself to answer questions of existence. That's not your job, that takes care of itself. Your job is to be part of life, and walk your path, that's all you have to do. You will find yourself along your path as you walk it, don't rush it or push it. You feel lost but I think that's simply because you're not looking at the path or what's around you, but only in yourself. When you look too far and too deep at yourself, you stop walking and get stuck there and confused.
Therapy would help a lot. You need someone to help anchor you and get you out of your own head and to learn how to do this. Give yourself time and be gentle with yourself.
I also read that deja vu can be induced by scientists on people so it is just a sense of perception that your brain has. It doesn't mean anything at all but your brain just had a little sensation of being familiar with things when it isn't. This can confuse you but remember, it can be induced so it is simply a brain malfunction for the moment. We all get it sometimes, and you're just having it a lot because of your focus.
I used to get this sense that I was deep back in my head looking out from almost behind myself. I saw everything like I was disconnected from it -- they were over there, I was over here. Derealization, depersonalization. It comes from anxiety.
You're going to get through this. You're not hopeless at all.