Well my recent experience of basically crumbling post preg led to a diagnosis of hypermobility syndrome. I saw a chiro, an osteopath, an nhs physio and finally a private physio who specialises in sports physio but I asked about hms (it was through my work insurance, teaching)
Nhs physio was a godsend at the time to help tape my back up as I was in so much pain. Also regarding CFS style pacing at the time as I also had thyroid and anaemia issues.
The osteo was quite a bit better than the chiro who poked and crunched me and tried to make me go back several times a week. The osteo at least have some exercises, but they're all different I guess, including the physios.
The latest physio actually has been the best. He worked in nhs originally. Joints etc are loosened by pregnancy and if periods have returned you'll be getting another dose of relaxin each month which won't help.
He diagnosed spd (Si joint, not at front) on top of the hms and showed me how my shifted pelvis was affecting my upper back. He also showed me how my core was affecting all of this by being weak. He's given me some really intensive, hard exercises which I've noticed are really helping, as well as a kind of constructive rest thing (Google it) but with a rolled towel between the shoulder blades to help loosen my now rigid upper back, which has been compensating for the overly loose pelvis. Lower back stiffness was the overly loose joints trying to hold them selves together in absence of a supporting core.
I have found really understanding all this the most important thing - his exercises have had the most impact in the shortest time. He also manipulated my pelvis as did the poking thing that the chiro did but to every vertebra, to help loosen it.
Imo and ime a really good physio will be worth weight in gold. Also could diagnose actual disc issues etc.
The hypermobility syndrome diagnosis has also been useful from the gp pov. It's often triggered by pregnancy. I was very into martial arts, swimming, dancing etc and good at yoga as I was flexible. Had no idea it could also be so debilitating!
I'd recommend getting into a pilates course asap too, and keeping it up.