I can offer some general information.
The feelings you described, such as the sensation of being watched, chills, and the belief that an entity is behind you, are often associated with paranoia and anxiety. Paranoia is a symptom that can be linked to various mental health conditions, including anxiety disorders, schizophrenia, and certain other psychological issues.
It's important to remember that these sensations and beliefs might not necessarily reflect reality, but they can feel very real and distressing to the person experiencing them. If you are genuinely concerned about these experiences or if they are causing you significant distress or impairment in your daily life, I strongly recommend seeking help from a mental health professional.
A trained mental health professional can conduct a comprehensive assessment, provide a proper diagnosis, and develop a treatment plan tailored to your specific needs. Remember that seeking help is a positive step toward understanding and managing your emotions and experiences better.
It's important to take your mental health seriously and not be hesitant to reach out for professional support. Many mental health conditions can be effectively treated with appropriate interventions, therapy, and sometimes medications, if necessary. Your well-being is essential, and there are resources available to help you navigate these experiences and feelings.