The answer to 'how did pest get in my house' is that pests can enter your home through a variety of ways, such as cracks, gaps, and openings in the structure. Common entry points include windows, doors, vents, pipes, and even small holes in the foundation or siding. Pests are looking for food, water, and shelter, and they can squeeze through amazingly small spaces to gain access to your home.
Some common signs of a pest infestation include seeing the pests themselves, finding droppings or nests, noticing chewed or damaged items, and hearing strange noises. The best way to prevent pests from getting in is to seal up any potential entry points and eliminate sources of food and water that could attract them.