I had SPD so horribly with my first, and it was made SO MUCH WORSE by bedrest (9 weeks side-lying).
I've had touches of it here and there this time, but nothing like last! Again, though, the week I spent on strict bedrest made it much worse.
The chiropractor definitely helped - is yours doing adjustments of the pelvis, specifically? The one I saw last pregnancy never did more than the activator on my pelvis. The one I'm seeing currently does the activator and also adjusts. She showed me how to adjust it myself as well (though it's more effective to have someone else to it!).
I also was taking daily baths when it was bad last time, and stretching my hamstrings and low back while in the bath. Basically, sitting in the warm bath and trying to touch my toes.
Also, when you go to get up from laying or sitting, first squeeze something between your knees. You can squeeze and pillow, or put two fists side-by-side and squeeze them. This will give you a little relief.
As much as it hurts, try to keep moving a little while being careful how you use your legs/feet. Just walk around a little to keep it from locking up. Bedrest really was brutal for it!
Also, I was on strict side-lying bedrest for 9 weeks, baby engaged for 5 weeks and made the SPD worse on the side where his head rested, I ended up with little use of my left leg because of it during labor. I had magnesium, I was bed bound, and I had to deliver flat on my back.
I still delivered 8lb, 7oz DS vaginally.
It'll be ok in that regard!!!