FYI, “fiancée” refers to a woman, and “fiancé” refers to a man.

This would be called Emotional Detachment or Emotional Blunting. It is associated with several mental health issues, such as anxiety, depression, and schizophrenia, and it can be developed as a coping mechanism for a stressful or abusive childhood or past. It can also develop as a side effect for some medications, so it could be worth looking into a change in prescriptions if you think that could be relevant.

That is to say, it is an abnormal mental state, but you are not unique in this mindset. You should strongly consider reaching out to a mental health professional to see if you can work on this as it is likely to lead to more isolation and a worsening of your overall well-being.