Help! Gnats all over my home and I don't know why!

I have noticed a significant amount of gnats flying around my home. I don't know why or where they are coming from. I don't have any plants or pets, I don't have any food sitting out or yet alone any rotten or spoiled food. My trash cans are empty, dishes are washed, and I am still seeing these annoying little pests! what can I do to get rid of them if I don't know where they are coming from or why? I set out little homemade traps with apple cider vinegar and dish soap, but they only do so much.