If your consciousness is created completely by the interactions of molecules in your brain and nothing else, then it would seem that all that is needed for you to exist is something like your brain. It doesn't have to be the same molecules, as those can be exchanged and the functioning continues. It doesn't have to be your complete brain, as you continue to exist after a brain injury. You can lose much of your brain, all of your memories and the ability to form new ones, and still be conscious, even with a different personality. You can take drugs and experience vivid altered reality and consciousness. When you sleep you have altered consciousness/reality. Perhaps if we had sophisticated equipment we could completely alter your memories or give you the memories of someone else. You have had conscious states since you were an infant, possibly at times in the womb, so you don't need your memories or knowledge for you to be conscious. So I don't see if materialism is true what this thing is inside your brain that is uniquely you that cannot be recreated in another brain. If we recreated a living brain just like yours after you died, would you come back to life? How much would it need to be like your brain to bring some of your consciousness back? The universe is huge and goes on for a long time and there could be a lot of brains very similar to yours way in the future or in the past.
It is possible also according to special relativity that the universe does not have a privileged "now" or present moment of time that applies to the entire universe. The material of your brain is spread out in four dimensions of spacetime, with the past, present, and future all existing eternally. A block universe view. The universe is not annihilated every moment and recreated slightly differently each moment. It persists and your consciousness would exist with it. If that is the case, then it seems that you have a perfectly good functioning brain exactly like yours at this moment--which is in the past or and future of other moments--that always exists in the universe. It does not seem that you could ever be dead or nonexistent. Your body might not exist beyond your spacetime, but that doesn't mean you continue on in a state of nonexistence in the worlds of other people. You might go on in another universe too, if the multiverse view of quantum mechanics is right. Infinite copies of yourself. Omg. It doesn't seem that we could ever escape this bizarre existence thing. And we don't know that we haven't always existed in some form. If there is some sort of stream of consciousness that moves through lives, before this life it is possible that I might have experienced your whole life and you will experience mine after your life. I usually do not seem to have the (normally conscious) access to memories of other lives or the future, although I may have lived through it countless times.