Pelvis Grinding

It's hard for me to look this up because it's not painful or anything. Twice, I've just been standing, and my pelvis makes this weird grinding noise, and then a quick popping noise. It's not painful, it just feels and sounds weird. I'm 36 weeks today, and the baby has starting moving a lot less. Is this just him wedging down or something? I'm pretty sure he's already dropped cause I feel a lot more pressure in my pelvis while walking and such. The grinding noise is just weird. It doesn't happen when I walk, just a few times when I've been standing still.