If you haven't considered it yet, I'd find a good osteopath or chiropractor who has experience in treating women in pregnancy or with SPD. They might call it pubic shear. But anyway, that is what helped me during my last pregnancy.

I had SPD in my last 2 pregnancies. Was in agaony for most of the second, wasn't so bad and I was able to stay mobile for much longer with the second. In part because I did start seeing an osteopath regularly before the symptoms appeared, and once my body recovered physically from the pregnancy I saw her again several times just to make sure all was going back the way it should be.