Never ending burnout

Hello. I have ASD, and I also suffer with pretty intense anxiety and PTSD. Lately I have been suffering what I’m pretty sure is autistic burnout and fatigue, something that’s left me bedridden on some days. I get out of bed, do something, not even something major and I feel like I just run 5k! I end up feeling dizzy and like I haven’t slept in days.

I have seen the GP about these, bloods etc showed nothing of concern. Her advice is to rest when I need to and do little things when I can. But it feels like such a waste of life, I’m here, functioning, existing… but not really living. It’s a strange situation and one I have never experienced before. Reading through NAS’s advice & guidance pages I think it is burnout, sounds similar anyway and I’m aware for some as we get older – I’m 27 now – our symptoms of anxiety and the way autism can affect life can become increasingly more difficult to cope with.
The advice & guidance has been helpful but I thought I would ask here too in case anyone has been through this or is currently experiencing it and might have any advice on what I can do to help myself.

Any advice is welcomed and will be helpful. This burnout feels never ending and is affecting my life in so many negative ways.

TIA x.