Existential Crisis...?

All seriousness now...

So i think i am having an existential crisis.

Sometimes i'll go through a stage where I have really deep thoughts that are quite scary.

The reason I think I am having one is for a number of reasons.

1: I become aware of other people's existence.

2: I and everyone else is gonna die one day.

3: There are going to be millions of years more after we die and it's going to be like nothing to us because we'll just be living in a black abyss of nothingness.

 4: Whenever someone brings up the subject of death I (for some reason) become feeling really uncomfortable or just feel like crying.

5: I realise that life is short (even though we can live up to 100 years old these days) and i don't want to waste anytime, i want to go on adventures and do crazy shit before it's too late.

6: I'm more aware of how fragile life actually is. I could be walking down the street and a freak accident could happen and i die.

7: Along with that i've become more aware of the side effects of drugs, alcohol and other things that go along with that and could damage so much of you later on in life, like you could potentially become brain dead or something.

8: When people say they hate life and they want to die, I feel obliged to give an inspirational speech on how much life matters and there's so much to happen in life.

9: Us as a planet are not even the size as a spec of dust in our universe and if the world were to blow up it really wouldn't effect anything. I'm basically an object that takes up empty space that is needed to be filled.

I mentioned something to my mum about this and she said 

"you're 15, you are not having an existential crisis" 

But i'm not sure if it's just a phase i'm going through or if it is normal to have these thoughts. 

To be completely honest the first time i started thinking about death and the abyss of nothingness was when I was nine years old. Every night for a month i'd get out of bed at 12:00 at night and run to my mum crying because i was scared of dying and since then it's been on and off and will just come at any random moment.

So if you know anything about this (if anyone see's this) or are maybe going through the same thing could you please tell me some information or anything please?

Thank you 

Bye