Sometimes I can feel the emptiness of our existence, is emptiness just a feeling or is the truth?

Its your friend....

That feeling is the doorway into all that you hope for and want out of life, it is your teacher, calling your attention to what needs to be done. That feeling of emptiness will lead you to the truth which will set you free.

You might appreciate Tanabe's Philosophy as Metanoetics,

Eugene Rose's Nihilism,

Omraam Aivanhov's Man, Master of His Destiny, and

Mark Prophet's The Path of the Higher Self.

One's perception of existential emptiness is state-specific, and meditations on the "positive negation" of e.g. Mulla Sadra and Saint Teresa of Avila (Interior Castle) are relevant.

Even physics has found no real emptiness (even the vacuum is teeming with virtual particles which sustain electrons in their orbitals; without them, the universe would collapse). Henry Stapp (The Mindful Universe) and Return to Life, Tucker, also helpful.

Emptiness is both a feeling and a truth. It's a feeling when you are hollow, and a truth when you can't get a sight of the stuff you want to do....

The feeling of emptiness is a world view choice based on conditioning.

Existential despair!

(Read Nausea by Sartre)

I would argue it is just a feeling, however. Emptiness is incomprehensible since it suggests nothingness which is incomprehensible.

Existence is filled with essence.

Feeling empty means you need a **** to fill you up.

It's only your perception. You are probably depressed.