Persistent feelings of disconnection from oneself is called derealization. Everyone has moments when they feel this way. But when the feelings are recurrent and distressing, it can lead to derealization disorder.
However, derealization is usually triggered by trauma or the use of illegal drugs. You report that neither is part of your history. Another common trigger is anxiety. It’s possible that an untreated anxiety over time can result in the feelings of disconnectedness. Complicating things further is that anxiety about the feelings (anxiety about the anxiety) can cause symptoms to be worse.
One other possibility is that a person has an unrealistic idea about what to expect from life. Our satisfaction with our life is a function of our expectations. If expectations aren’t being met, people sometimes mistakenly assume that there is something wrong, that things aren’t “real enough”, not that they expect too much or too little of life.
Without talking with you, I can’t assess which, if any, of these possibilities apply to you. I therefore urge you to see a mental health professional for an evaluation. What have you got to lose except an hour of your time? It may be that such a meeting will find that your feelings are quite normal for your age and that you will gain peace of mind. It could also be that you have more anxiety than you are aware of and some treatment will be recommended. If so, you’ll have a better understanding of yourself and you will know what you need to do next to help yourself.
I wish you well.