32W1d ftm here. I know your pain. I feel it every night, several times a night. Shanz is right, hips spreading have a lot to do with it. Constant flipping is the only thing to relieve it immediately. You're so close to the end idk if spending 40-80 on a boppy pillow is worth it. But I DO have one and it makes a world of a difference for sleeping in general, not too much for my hip pain though (it does support the belly which might take pressure off) . I def would recommend u sleep with a pillow between your legs at least.
From what I've been told this is most likely your hips spreading preparing your body for delivery. I haven't gotten that far so not speaking from personal experience here. Try getting a body pillow or putting a pillow between your knees to see if that takes some of the pain away. If it's so bad you can't walk I would consider a call to the dr or even a chiropractor for a gentle adjustment of your hips