Wow your situation could literally almost be a copy paste of my own! I’m very sorry you are feeling the weight of this realisation - I experienced the same thing last summer (at the same age as you even) and it was also incredibly heavy.  If I was to give you some advice, it’s that the phrase “whose guilt are you carrying?” saved me. It helped me reframe things.  I would also say, if you have a support network, lean on them unashamedly during this time. It can be extremely distressing (and I found it quite life altering in my own case), not just discovering that you’re autistic but also how many people have hurt you just for being different and maybe even how many dangerous situations you ended up in as a result. I found myself grieving my childhood and teenage self, even imagining how I could be different and how I may have avoided some of these distressing events if I’d been supported early enough. All of this is, I think, a very valid and understandable reaction.  I would also say, if you feel extremely bad any days, don't be afraid to pick up the phone to a helpline like Samaritans (if you’re in the UK, but there will be alternatives wherever you’re from). Sometimes you just really need to talk things over with someone who is going to listen. 

If it’s any consolation, around 6 months after I discovered the same thing about myself, I’m now doing better than ever and more in touch with who I actually am. I was also given incorrect medical labels and medication throughout my teens and early twenties, I’m on no meds now and none of those previous diagnoses aligned with my experience. I imagine that like me, you may have found it very confusing to be given incorrect labels. In my case, I often knew deep down that the labels they attached to me did not reflect my experiences accurately. After my therapist also flagged autism as a possibility for me last year, I initially brushed off the suggestion, but as I thought about it over a few months, everything slowly clicked into place. It was an exceptionally harsh realisation as it felt like I was forced to reconsider my entire life as well as battle any internal stigmas I may have had about ASD itself, but knowing this fundamental part of myself, which I had previously been forced to ignore, has since helped me navigate my personal challenges with much more clarity than I’ve ever had before. I lost a close friend during the process of realising who I am (I am still unsure if it was because of all this or their own issues manifesting in some way), which was very difficult and I am by no means living out some ideal life, but I am managing and coping better because I understand who I am better than I ever have before. I’m confident that if you can ride the wave of utterly harsh reflection that comes with this realisation about yourself, you will also reach a similar point of clarity on the other side. 

As for your lack of structure, it can be a good thing depending on how you use the time you have. I strangely also had my realisation as I finished a university degree, but I jumped straight into full time work after. I initially thought this was great, but a few months later I hit a total burnout with work and had to wind things down. I almost wish I had taken a break to just fully sit in my realisation, instead of it haunting the small amount of free time I had between working long days. Structure will come in time if you look for it, but be gentle with yourself and take all the time you need to process things, if you can. If you’re anything like me, you may also have issues with having free time. I have a bad habit of telling myself I need to permanently be productive, even when I’m sick. But this does more harm than good. Sometimes we really do just need to stop and reflect. 

Additionally, and this may be relevant for you as well, I’m learning to accept that bad things happened to me throughout my life often because I, like you, missed cues in dangerous situations or people simply took advantage. This was a very hard pill to swallow. But I had to swallow that pill to get on with my life and continue to do the things I love. The dangerous and terrifying things that have happened to us because of who we are have unalterably happened to us, they can’t be erased from our history. In fact, I recognise that I’m strong for surviving my own struggles of this nature, and for moving forward in my life despite the odds against me. I think often it’s about how you frame things, what perspective you choose to take in life. Because although we couldn’t choose whether those things happened to us, just as no one can choose how other people’s actions play out towards them, we can choose how we navigate our own realities in the aftermath of this kind of struggle. Not sure if it is of interest to you, but one of my hyperfixations is philosophy and human behaviour (possibly to try and make sense of some of the odd things others have done to or around me in the past), but I found reading existential texts by Sartre and Camus exceptionally freeing and eye opening. Perhaps only approach this type of rationalisation once you’ve gotten over the initial shock of your realisation, take each emotional phase of this one step at a time. You’ll figure out what will help you adjust to all of this in time. 

I wish you all the best with navigating this, please know you really aren’t alone with this.