I can suggest some potential reasons for such feelings:
Identity issues: Sometimes, people struggle with their identity and sense of self. This can lead to feelings of detachment or a sense of not belonging, even to the extent of not feeling fully human.
Depersonalization or Derealization: These are psychological phenomena where individuals may feel detached from themselves (depersonalization) or the world around them (derealization), leading to a sense of not being human or not belonging to reality.
Existential thoughts: Deep contemplation about existence, life's purpose, or the nature of reality can sometimes lead to feelings of dissociation or otherworldliness.
Mental health issues: Certain mental health conditions, such as dissociative disorders, depression, anxiety, or identity disorders, can cause feelings of detachment or estrangement.
Spiritual or philosophical beliefs: Some spiritual or philosophical beliefs may challenge conventional notions of what it means to be human, leading to feelings of being different or not fully human.
Metaphorical expression: In some cases, the feeling of not being human may be a metaphorical way of expressing emotional or psychological struggles.
If you're experiencing these feelings and they're causing distress or impairment in your daily life, it's crucial to seek support from a mental health professional. They can provide a proper assessment and offer guidance or therapy tailored to your specific needs.
Remember, it's okay to feel different or have complex emotions, but seeking help from a professional can assist you in understanding and managing these feelings in a healthy way.