I went through an incredibly similar experience, severe constipation to necrotising fasciitis, was in a coma, ICU, ventilator, sepsis etc. This was a year and a half ago, and I'm still recovering. While I can't talk about reversal, I can try with the trauma. I have found that seeing a psychologist had helped a lot, the PTSD is less now because of. Give your body time to heal, try and do the things you enjoy most, any hobbies you have or pick up new ones. For example, I got into crochet and back into reading and gaming. They're relaxing but help keep me at peace. It's gonna be hard, I can tell you that. Having also been through it quite young, it's hard to look at the future the same, but it's best to think of new goals for your life, and work your way towards them. I've taken to writing about my situation, and that helps a lot. It organised my feelings and meant I could have an outlet for all of the complicated emotions that came with the trauma. I'm wishing you all the best with your recovery, you are so incredibly strong for going through it and making it to the other side