You miss a couple more questions, from the opposite direction. These questions are:
1. Does the universe exit?
2. Does life exist?
The reason why these are important is, nobody can prove them with solid, empirical science.
Big Bang is a fantasy that sounds good to those who need it to believe in. But the science behind BB is so extremely lacking that it is really utter foolishness. Besides, asking any layman to understand the little science there is, makes the whole topic of this question in a public forum to be foolishness.
As far as life goes, the dividing line between something that is dead, and the moment before while it was still alive, hasn't been found. If it is close to being found, it is understood (almost) by a few technical people, but absolutely none of us lay people.
The point of asking these two additional questions is, before we ask about some fanciful place called Heaven, we really need to be afraid, because we don't really know anything about this age.
But take heart. Since this universe and life seem to exist without proof, and without the knowledge of how such could be possible, something like Heaven could exist for the same, unknown reasons.