Embattled Backstreet Boysalum Nick Carter has been diagnosed with post-traumatic stress disorder – and a therapist believes the disorder is the result of the sexual assault allegations against the singer. New court documents show the 44-year-old songster was diagnosed with PTSD after one of his alleged victims, Melissa Schuman, 39, first accused Carter of sexual assault in 2017. Therapist Geri Smith told a court while testifying in connection to the lawsuit against Carter: “I had a therapy session with Mr. Carter, and I learned that a woman from his past, Melissa Schuman, had recently accused …