I suggest you bite the bullet and go to a chiropractor that works on pregnant women. My spd was so bad that I couldn't move for a while. I couldn't even clean the toilet for 2 weeks (normally I clean it at least once every few days because DS is experimenting with peeing at different angles when no one watches him).
After 5 treatments, I finally saw marked improvement. It still hurt, but not even close to how bad it was. Now that it's been 10 weeks or so of treatments, I am actually walking up and down stairs (at 38 weeks). It hurts to change position while lying down and it hurts when I'm sitting, or at times walking or standing, but still, WAYYYYY better.
Unfortunately, now I'm super out of breath doing even the slightly thing, so I still have to go slow.