Being dead is nothing to be scared of mate, once it's happened you won't know or feel anything.
Being dead is neither good nor bad, as it's simply just nothing.
It's hard to fathom being dead but that's just the way our brains have evolved.
The only thing to worry about is if you're in pain before you die but there's plenty of pain that you will experience and survive throughout life, as will we all, so even that's not worth worrying about. You don't worry constantly about stubbing your toe or getting kicked in the bollocks do you?
As others have said this will pass, I thought about it similarly a lot when I was younger for a period but I quickly stopped.
Life is short mate in reality but it's all about just getting enjoyment out of it whilst making a positive impact for others and leaving a good image of yourself behind.
Stages come and go and in 5 years time it may be your latest gas bill that worries, hopefully not but that's life.
Watch the shawshank redemption if you haven't already.
Sorry to hear about your brother by the way.