Nightmares

Autumn_

I have nightly nightmares that affect my ability to function the next day... I remember them in vivid detail and certain images pop up in my head at very unconventional times and makes me feel afraid or sad. I'm 18 and I refuse to watch any terrifying shows or movies because of this (and I hate horror just in general) I've talked to my therapist about this but I'm getting more questions than answers. Does anyone know what this could possibly be or how I can stop it? I'm terrified I'm just going to be doomed to have these nightmares...