I completely get you.
I have had this feeling for... well, as long as I can remember tbh. I think about the same stuff a lot.
I often come to the conclusion that we are so tiny, insignificant and meaningless that nothing actually matters. We're all gonna die and be forgotten in time.
And this fact really makes me upset and angry because we can't do anything about it. Literally nothing.

But.

Living your life, going out to school/work everyday, interacting with others, etc. is literally the only option we have, the only thing we can do. There is a strange reason that is driving us forward in time, the same things that make us (or most of us, at least) not sit at home locked up in our rooms in the dark, awaiting the end.
Something that makes life worth it. Something that makes us bothered to do things.For example, meeting people even though we'll all be gone in time. Loving people even though it will hurt us to lose them.
We as people have this natural instinct to always survive, for as long as we can. Why? We're gonna die anyway right? Still do it.

And honestly, while thinking about existence and meaning, asking yourself 'why?', ask yourself 'why not?'.
Because it's all we can do. That's our task, to make existence mean something, and be worth it.