OCD and PANDAS Mama -- Our successful antibiotic was Augmentin XR.
Regarding psych drugs, I agree with you completely in terms of working on the medical issues first as best you can. We, too, initially had a psych who was all to willing to increase SSRI doses, add other meds, change meds, etc. at all too rapid a pace; like you, we trusted him because he was supposed to have the education and experience. But I think some have either been at it way too long and are now just going through the motions, with a tendency to push whatever the pharm sales rep most recently dropped on them, or they just want to satisfy distressed parents who want SOMETHING that will help their kid be more functional or compliant or calm or all of the above. I truly shudder when I realize what we put my DS's brain through, with this quacky psych messing with his medications as though there would be no repercussions.
Once we found PANDAS and started antibiotic treatment, we were able to find a psych who had some PANDAS knowledge, but more importantly, she was intellectually curious and kept up with ongoing research, etc. So she was far more thoughtful and cautious in terms of treating DS and introducing or changing meds.
I realize that implementing psych meds during or even following PANDAS medical treatment may "muddy the waters" in terms of completely addressing and/or eliminating the underlying culprit, but we chose our path because our DS was older, had been dealing with all of this longer, and wanted his functionality back almost as much as we wanted it for him. So the psych meds were an important part of that for us. If you decide to return to that route at some point, I would just encourage you to not be shy in interviewing prospective psychs; make a list of pointed questions to go in with, and get some answers. And then you and DD be proactive and participatory in any treatment you undertake in the future, rather than just accepting that because they have a certificate on their wall, they have all the answers. Clearly, they don't. As my dad used to say, "They call it 'practicing medicine' because they're practicing on US!"
All the best!