I think I have possessive personality disorder, is that a thing? I mean I am so obsessive over some people or things sometimes that I cant think of anything besides them, and then I think its love, but its not, its just obsession, and I become too possess

Relationships.. Sounds like you're trying to figure out why you act the way you do in a relationship, which leaves you disappointed. If you think you could use some professional help or therapy, talk to your parents to see if they agree. If you prefer, talk to a school counselor or social worker to see if they think you might benefit from help being too "possessive" of some people. Take care.
Personality disorder. It isn't a name in the DSM V, but more important is what are the symptoms or behaviors that you believe you need to change? These are learned responses, sometimes to early life abandonment or role modeled behavior by a parent. Please talk to an experienced Psychologist or Psychiatrist for your options for therapy and/or meds. That you are asking is a sign that you are capable of change!