Sounds more like schizophrenia or anxiety. Without knowing more, I couldn't offer any more insights. Are you actually SEEING a monkey? Are you taking anything? Has this happened before? Do you ever hear voices or think people are out to get you?

If this is a real problem and not a narrative, I would see a psych and try to get to the bottom of it. Whatever it is, it is treatable. Don't give up hope.