Fiddlegrl -- Welcome to the forum, though I'm sorry for all you've been through and the issues you're still fighting.
I will say that I've been with this forum for many years now...first during my DS's illness and healing, and then somewhat less frequently for the last few years, checking in to follow up on old friends and any new research, and to chime in when something resonates with my experience. Pretty much ALL of the symptoms you've described, unfortunately, have been discussed here as part of the PANs/PANDAs continuum. It stinks.
I don't have any practical experience with respect to Lyme and its co-infections; my DS's syndrome was clearly strep-related, though seasonal allergies exacerbated inflammation and the immune response for a number of years, once the PANDAs had kicked into high gear. Like you, though, we believe his behavioral issues were tied to atypical strep infections potentially as young as 3 years of age, though certainly by the age of 6 when he was officially given an OCD diagnosis. But he never tested positive (via swab and culture) for strep at the time, and no local doctors would give us the time of day regarding PANDAs then, either, so he went without any real treatment until he hit 12. That's when the PANDAs brought him to an absolutely non-functional state, the research coming out of NIMH, Columbia and Dr. Cunningham had progressed, and we were finally able to talk someone into an antibiotic trial. It was a long road, but the rest, as they say, is now thankfully pretty much history.
As a result of our experience, though, I do think it likely that PANDAS/PANs sufferers who are at a more advanced age before receiving immune and/or anti-inflammatory therapies may have a harder road with respect to healing and "bouncing back;" not sure if that's because the brain "wiring" has matured more in the interim, or if the chronic inflammatory and auto-immune responses in the body are somehow more entrenched and therefore harder to reverse. In the end, it took my DS about 5 years in total to return to pretty much full functionality, and that was with auto-immune, therapeutic and psychiatric interventions all thrown into the mix. He continues to contend with some OCD and situational anxiety now and again, and I'm not convinced that this will ever disappear completely. But those issues remain at manageable levels (knock on wood), and he's happy and healthy and constructive and functional. Pretty much all we could ask for, after what he went through.
I'm not sure how to advise you on any possible next steps, really, except to suggest that perhaps exploring some additional genetic markers and methylation issues might help you for the long term? You mentioned genetic testing for porphyria, but did you get a full work-up? A search here on the forum for "methylation" and "mutations" will lead you to multiple discussions regarding the methylation cycle and how genetic testing has helped point some families to a regimen of supplements and/or medications that proved to be more effective for them in light of various mutations and genetic predispositions. Perhaps that's worth a try? Finding a well-versed LLMD and/or integrative physician who could be your partner in working through these issues would be a bonus.
Your post was very well-written, so I'm picturing an intelligent, capable and fairly "together" young woman, so I sincerely hope you're finding moments of joy and contentment in your everyday life, despite this tremendous burden. All the best to you!