by actual universe, I meant total universe ( opposed to the observable universe). All of the evidence we have collected so far suggests that the universe is flat and infinite. While some finite universes could be proven, so far we have not.

Isn't space itself continuously expanding?

Expansion of space doesn’t preclude the universe being infinite.

what's the proof it's finite?

Our senses are finite; we cannot directly know infinity through them. Because of that, I think the burden of proof is on the claim that it is infinite.