Why....?

It's probably the most normal thing for people to question. Questoning of this depth shows that you're a deep, thoughtful person, more in tune with matters deeper than those which bother other people.

Where people come from, why they are here and what is the grand design, if any? Are there other worlds like this one and will everything, ever, become clear?

Don't worry whether or not these questions you ask yourself are normal, just keep asking them. They may never be answered at all, I'm sure you know. There is nobody who is capable of answering them.

That's the trouble with difficult questions, they're not easy to answer.

That doesn't mean, of course, that we shouldn't ask.

Deep thinkers unite. (: I think about this all the time. It's good to want a purpose.

It's totally normal. Most people at some point question why humans exist or why they, themselves exist. People throughout time have tried to answer that.
The point is, you're not the only one, and it's totally normal.