Bed Bugs
In case you've never seen them, bed bugs have a very distinctive size and shape. They are brown with an oval body. Bed bugs' body varies in size depending on when they had their last meal. And, their bodies are flat, which means that they can squeeze almost anywhere. However, because they are about the size of an apple seed most often, you will likely not be able to make out too many details. If you have moving black/brown dots on your bedclothes, then you have a bed bug problem and need to call a bed bug exterminator.
Thankfully, bed bugs prefer to infest beds. Mattresses, box springs, headboards, and bed frames are their preferred habitat because they are parasites that feed on humans. But, keep in mind that while it's true that you will most likely see bed bugs infesting a bedroom if they are in your home long enough, they will move to other areas. Therefore, you need to get bed bug treatment as soon as possible to keep the issue localized.