I think we're getting to quibbles about what the word "believe" means. You can believe in scientific theories, and you do; to the extent that you are prepared to bet your life on it. Don't fly or go climbing if you don't believe in gravity. Which is a case in point. We have a perfectly functioning theory of gravity, which you can take at many levels, Newtonian or relativistic, as it is useful. But we really have little idea of the mechanism of gravity, and there are bound to be changes to existing theories when (if?) we manage to combine relativity with quantum mechanics. And when we do that, nothing is more certain that the new theory will raise a whole new set of questions.

So in reality you never get to the truth, and you might question if the word "truth" actually means anything specific. But if the alternative is shutting down of the intellect, and refusing even to ask the questions, in my opinion it's better to learn to live with the uncertainty.