Im 39 weeks tomorrow and I have been going through the same thing since 37 weeks. Pillows didn't work for me. I honestly just tossed & turned. Propping myself up and sleeping on my back was the only helpful thing for me. Baby is getting ready... That's the only thing that keeps me sane. Goodluck!
He's been head-down since last month. He's actually been way low pretty much the entire pregnancy, which is why I had so much pelvic pain throughout pregnancy. But I tried putting a pillow between my legs & even under my stomach. It only helps on occasions. :/
Its usually just the baby dropping down into your pelvic area and pressing on nerves. Im 35 weeks and i have the same issues. Try taking a warm bath or laying on your side with a pillow wedged between your legs to prop you pelvis more