Interesting question. One could flip it ("How do you know God ISN'T telling YOU something?"), but that then begs the question "What is the nature of God's communication?" Everyone has an opinion. Atheists must if they are going to try to explain such a phenomenon away, and theists must if they believe God reveals anything at all to them.
So what works for you? Ecstatic visions? Physical voices? A sense of being directed or led? Something similar or totally different?
Here's a possibility upon which anyone who is genuinely interested in the question and not their own certainty nor simply being argumentative can reflect. I offer it with no expectations or defense:
Perhaps (merely perhaps) this is what God is saying...
The birth and death of stars and galaxies. The spark of life appearing on various worlds. The fire of chemistry and biology spreading across these worlds, changing and diversifying. The emergence of forms of this blazing process that are self-aware and able to perceive in new ways like their ancestors who developed photosensitive cells. The sun rising and setting. The song of the bird and the whale. Emotion, cognition, and reflection. The way parents are always parents in every culture. The smell of a happy puppy waggling its little tail. All thirty one flavors. The people and events in your life. Your reaction to reading this. The part of you that is constant no matter how you change physically, mentally, or otherwise. This moment, eternal yet ever new.
(To borrow from the UCC, "God is still speaking...")