I agree. In some cases, one does not need a dx. I can relate to your experience as my experience also includes sexual abuse (childhood and during adolescence). And when I was 12, I started having nightmares and flashbacks during the day; when I was 13, I stopped touching or hugging anyone, including my family; and worst of all, I attempted to take my life as I was unable to manage the memories.
Did I need an official dx to know what was going on? No, of course not.
I sought help when I was 24 and I was immediately diagnosed with PTSD. The only reason that I sought professional help was so that I could navigate the healthcare system and recover. I do not need a professional to tell me that I have PTSD.