Is there no randomness?

I've been thinking.
I talk so much about being able to choose.But now something in my head ,I really can't escape thinking.
About physics and maths.
If we trace down everything, I think it will end in physics and mathematics.
If I can really put this right.

Consider pool. By using physics and maths we can calculate what the strike will result to.Where each ball will be at the end of it.
So probably, it can be calculated how each molecule or atom, or sub- atomic particles or whatever, moves.Which would mean that there is no randomness.
I'm not really good at physics, and haven't studied much in maths. But even if you see chemistry, and even biology, the end point of an explanation will lead you to maths and physics.
Now this would mean, that there is no such thing as random.Everything happens as an effect of something.Meaning , nothing takes place on it's own.
I know it's theorotical, but if we could keep an eye on every bit of energy and matter in existance at the same time....we can precisely calculate what will happen next?
By using accurate maths and by knowing physics as exactly how it is considering every factor(even things we do not know of and do exist; because my point is not knowing what will happen next but that there is the absolute certainity of it that it will happen.)
This raises a question in my head, about our ability to choose. Are we even choosing because we are supposed to choose that? The chemicals in your head acting as an effect?
Is everything a destiny caused by something that always existed?
Is everything that will happen will be because it had to?

I don't know.It's a little uncomfortable idea for me.Though not too much. And I tried to avoid it because it is a contradiction to what I first thought.But it keeps coming back.Then again, it's in my own head.

That everything has a certainity.

That our choice and what we do is just an effect of something happening long long ago?

I don't really know.