Is it possible for ptsd to last for a little over 15 years, even if you only subconsciously remember the trauma?

The nature of PTSD: Not only is that possible it is the very nature of ptsd. It effects us on many levels for many decades unless one can deal with the trauma. That doesn't mean you have to relive it but it does mean that your brain needs to learn to reprocess it. Emdr will help with that.

Yes: Ptsd can last for decades if untreated. Fortunately, it is one of the most treatable psychological disorders. Psychotherapy using prolonged exposure or cognitive processing therapy has shown the best outcomes in the research (even over medication). A trauma psychologist can provide these treatments and refer you to a psychiatrist for adjunctive pharmacological treatment if appropriate.

Not clear: Reliving is or re-experiencing trauma (s), being preoccupied with it -is an essential feature of ptsd. This may occur through dreams, thoughts, memories, feelings, halucinations, physiologic reactivity. With out reliving in some form, the criteria for ptsd is not met. However it is not uncommon to be unable to recall major aspects of a particular trauma. Does this answer your question?