Ugh. So sorry you're dealing with this.
I had it post-partum with DD1 because of poor pushing position, and it flared up big time during my pregnancy with DD2. For me it flares up even when I'm not pregnant if I am not careful. I mentioned being concerned about it getting worse this time around to my MW early on in this pregnancy and she told me two things - when you walk, think of keeping your knees and hips closed, almost turned in; and sleeping, even when you turn over in bed, make sure you keep your knees together. I've been doing those two things this pregnancy and it has made my symptoms much better.
I was nervous about starting a yoga workout because I thought wide stance poses might cause a flare up, but so far, it hasn't...
I didn't get treatment from a chiro or physical therapist (I'd go the chiro route though, if it were me) but I have at least one friend who said chiro helped a lot. And as for the online horror stories...mostly SPD does resolve after pregnancy and in my case, even though it's persisted off and on between pregnancies, it's barely noticeable. I'm not combined to a wheelchair or anything. ;-)
and it was MUCH better post partum with DD2 (I think) because I used a birthing stool instead of being on my back with two nurses pushing my legs apart like I was with DD1. Talk to your mw about best pushing positions during labor.
Hope you get some relief!