Hare Krishna

[Kayenneh]

God has, historically, been a really popular answer

I have to quote one of our admins, Darwinian in this case: "If 3 billion people believed that 6+6=13 it still wouldn't be true!". Argumentum ad populum is a fallacy.

As an atheist, it seems to me that the least you're saying is "Well, I know the answer to all those questions isn't God." So then what - do you have a better answer?

No, as an atheist I say I don't know, but I''m waiting for proof. As long as there's no proof, there's no need for belief, but instead there will be someday knowledge.

As for answers to your questions, well:

"Why do I exist?" Because mum and dad had intercourse and their haploid cells were compatible.
"Where does everything come from?" From stars, actually. Without all the suns, the bigger elements wouldn't not have formed.
"Why can't I have or do whatever the hell I feel like?" You cannot have everything you want, because not all wants are achievable due to loads of factors. You can do whatever you want, but there will always be consequences. When you think the consequences are worth it, you'll probably do it too.
"Why do I have to die?" Because your body can't hold on for ever.