Body glide does definately help, but it really does sound like your boots are a bit on the large side.
I've had issues like you describe in footware that was too large, so my feet were slipping around
in them. In my case I have wiiiide feet, and a narrow heel - I would sometimes (stupidly) buy standard width footware and compensate for the width by buying larger sizes. The result was
never as good as a proper fit - which should not pinch your toes of course, but your foot should
also not be moving around in there. ensure you've got them laced up snug, but if you still get no luck you may need to consider a different shoe with a good snug (but NOT pinching - that's worse)
fit.