I have a problem where all my good memories turn into horrible memories. It's difficult to find any good memories. Is there anyway you can help?
You may be depressed. See your doctor and tell him more about the way you are feeling. Preferably a psychiatrist. Sounds like you may benefit from antidepressant medication and/or psychotherapy.
Past trauma. You may have suffered some past trauma / traumatic event which is somehow modifying your memories. If so, you may have post traumatic stress disorder. This condition is often marked by vivid memories of he trauma ( flashbacks), nightmares, and exaggerated startle response. See a psychologist or psychiatrist for an evaluation.