I feel like I can totally relate with you mate.
Usually we don't think of death as something real that will happen to us. We kinda "know it", we are "aware" of it, but I don't think most of the time we really understand what it means, that like any other day or moment in your life you've been waiting for, death will also eventually come. The hard part is accepting this "eventually" as real, and I myself can only sometimes achieve it for a brief moments in which my heart thightens in my chest, I get shivers and get lightheaded. It fades rather quickly though, as if your brain is applying some sort of self-defense mechanism to prevent you from having that enlightenment.
Now, what I've come to realise though is that perhaps I don't really fear death itself, but rather the unavoidable pass of time, i.e, change. Everything we know and love will eventually disappear. Life itself will also disappear, and then nothing else will come for the rest of eternity. When I think about that I get some serious anxiety. I feel like I need to be doing something else with my life, right now, in this precise moment, but I don't know what, which further aggravates the issue.
I cannot tell you how to overcome this, since I'm lost myself, but thinking about the alternative might be slightly comforting. Or rather, the lack of alternative. There is no point in between a finite and a non-finite life. Do you really believe thinking of an eternity to come would be less painful? An infinite time, in which you've already experienced everything you possibly could infinite times, and there's still an infinite amount of time remaining. Would you call that being alive? I could certainly tell that I'd rather be dead. For sure.
I know, I know, that is not really reassuring, it's equivalent to tell someone "if there is not solution to your problem, then why bother worrying about it?". But that's just the way thing are, for you, for me and for everyone that has ever existed and for those who are yet to come. What alternative do we have but to accept it?